Willis Tower

Sears, Roebuck & Co. had occupied an office complex on Chicago's west side since 1906. The existing offices were inadequate by 1966, prompting Sears executives to begin searching for a new site.{{cite news |last=Hoyt |first=Monty |date=May 25, 1973 |title=Sears Tower of tubes sets bundle of records: Unique structure |page=12 |work=The Christian Science Monitor |id={{ProQuest|511528132}}}} By 1969, Sears was the largest retailer in the world, with about 350,000 employees.Kerch, Steve (October 20, 1991). "This job is a tall order: Sears Tower project is the height of redevelopment." Chicago Tribune. Sears executives quickly determined that a new headquarters complex in the suburbs was infeasible, since it would require relocating about 7,000 employees. Instead, Sears executives decided to consolidate the thousands of employees in offices distributed throughout the Chicago area into one building on the western edge of Chicago's Loop.{{cite news |date=August 26, 1973 |title=The Tallest Building |page=L10 |work=The Washington Post, Times Herald |issn=0190-8286 |id={{ProQuest|148369539}}}}

Sears asked its outside counsel, Arnstein, Gluck, Weitzenfeld & Minow (now known as Saul Ewing LLP) to suggest a location. The firm consulted with local and federal authorities and the applicable law, then offered Sears two options.Arnstein & Lehr, The First 120 Years The first option was the Goose Island area northwest of the Loop, but Sears's vice president of real estate, Matthew J. Stacom, rejected this proposal. The other was a two-block area in the Loop, bounded by Franklin Street on the east, Jackson Boulevard on the south, Wacker Drive on the west, and Adams Street on the north. Though the site was more centrally located, it was also relatively small, with about {{Convert|55000|ft2}}. Bernard Feinberg, Albert I. Rubenstein, and Philip Teinowitz had assembled that site over the previous five years, but they had failed to acquire a neighboring {{convert|74,000|ft2|adj=on}} lot from bus company Greyhound Lines.{{Cite news |date=October 18, 1970 |title=The World's Tallest: Saga of a Chicago Skyscraper |language=en-US |work=The New York Times |url=https://www.nytimes.com/1970/10/18/archives/the-worlds-tallest-saga-of-a-chicago-skyscraper-worlds-tallest.html |access-date=September 7, 2022 |issn=0362-4331}}

Feinberg, Rubenstein, and Teinowitz then bought options for three adjacent lots. Under the terms of each option, unless the three men were able to acquire at least one of the lots within 90 days, all three options would be forfeited. Ultimately, Sears acquired the Loop site in 1970. Sears then obtained permits to close down one block of Quincy Street, which bisected the site from east to west. Attorneys from the Arnstein firm, headed by Andrew Adsit, began buying the properties parcel by parcel.Chicago Tribune, December 28, 2003. Sears purchased 15 buildings from 100 owners and paid the government of Chicago $2.7 million (equivalent to ${{formatprice|{{inflation|US|2,700,000|1970}}}} in {{inflation/year|US}}){{inflation/fn|US}} for the block of Quincy Street that was to be closed down.{{Cite news |last=Nagelberg |first=Alvin |date=July 28, 1970 |title=Sears to Construct Tallest Building In World, 110 Stories |pages=1. [https://www.newspapers.com/clip/108217507/ 35] |work=Chicago Tribune |url=https://www.newspapers.com/clip/108217480/sears-to-construct-tallest-building-in/ |access-date=August 24, 2022}}

Sears executives estimated that their new building would need about {{convert|4.2|e6ft2|m2}}, split into 70 stories with {{convert|60000|ft2}} each or 60 stories with {{convert|70000|ft2}} each. Sears commissioned architecture firm Skidmore, Owings & Merrill (SOM) to design the tower.{{Cite news |last=Nagelberg |first=Alvin |date=August 2, 1970 |title=Sears Tower: New Heights of Design: Will Blend Advanced Concepts |pages=97 |work=Chicago Tribune |url=https://www.newspapers.com/clip/108217158/sears-tower-new-heights-of-design/ |access-date=August 24, 2022}} SOM was also the lead structural engineer, and Jaros, Baum & Bolles provided MEP engineering.

Sears planned to move its merchandise group into the building initially, renting out the remaining space to other tenants until needed. Sears executives were accustomed to large floor areas of at least {{convert|100000|ft2}}, but SOM architects raised concerns that the large floors would be unattractive to smaller tenants. A subsequent proposal called for two buildings connected by a footbridge, which would respectively contain {{convert|50000|ft2}} and {{convert|30000|ft2}} on each floor, but this was also infeasible.

Some floors were designed with smaller footprints to attract prospective lessees, so the building's height was increased to meet Sears's floor-area requirements. Architect Bruce Graham and structural engineer Fazlur Rahman Khan, both of whom were partners with SOM, proposed a tower with {{convert|55000|sqft|m2|adj=on}} floors in the lower part of the building, as well as a series of setbacks with gradually tapering floor plates, giving the tower its distinctive look. During the design process, one of the architects reportedly pulled out nine cigars and staggered them vertically until the pair both agreed to the arrangement.{{Cite web|date=March 8, 2008|title=The Tallest Skyscraper - TIME|url=http://www.time.com/time/magazine/article/0,9171,907406,00.html|archive-url=https://web.archive.org/web/20080308034107/http://www.time.com/time/magazine/article/0,9171,907406,00.html|url-status=dead|archive-date=March 8, 2008|access-date=September 12, 2022}}{{harvnb|Pridmore|Larson|2018|ps=.|p=182}} This allowed Sears to occupy the large lower stories, while providing more conventional office space that could be rented out on the upper stories.{{Cite news |date=August 30, 1970 |title=Tower Will Withstand High Wind |pages=97 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109122999/tower-will-withstand-high-wind/ |access-date=September 7, 2022}} The firm of Saphier, Lerner, Schindler was responsible for determining Sears's space requirements and designing furniture for the company. It conducted a year-long study to determine how 16 of the company's departments should be laid out within the building.{{Cite news |last=Nagelberg |first=Alvin |date=September 20, 1970 |title=Building Sears Tower--A Real "Inside" Job |page=C16 |work=Chicago Tribune |id={{proQuest|169878110}}}}

As Sears continued to offer optimistic growth projections, the height of the proposed tower also increased. Under Chicago's relatively lax zoning laws, the site could theoretically accommodate a 300-story building with {{convert|13.5|e6ft2}}. In practice, most potential tenants did not want excessively high offices. Additionally, the Federal Aviation Administration (FAA) restricted the height of structures in the area to protect air traffic. FAA officials publicly denied that they had imposed a height limit;{{cite news |last=Martin |first=Paul R. |date=January 20, 1971 |title=A Rising Competition: It's Hard to Say Which Is Tallest Building: Trade Center and Sears Building Vie but Won't Admit It; Should a TV Tower Count? |page=1 |work=The Wall Street Journal |issn=0099-9660 |id={{ProQuest|133622903}}}} however, the area's minimum safe altitude would need to be raised by {{convert|1000|ft}} if the building was just {{convert|1|ft}} taller.{{Cite news |last=Arthur |first=Art |date=July 1, 1971 |title=Sears Is Now Tallest |page=A13 |work=The Austin Statesman |id={{ProQuest|1521729590}}}} Plans for the tower were announced on July 27, 1970. The {{convert|1450|ft|4=-tall|adj=mid}} building would contain 109 stories as measured from Wacker Drive and 110 stories as measured from Franklin Street.{{Cite news |date=July 28, 1970 |title=New Sears Building in Chicago Planned as the World's Tallest |language=en-US |work=The New York Times |url=https://www.nytimes.com/1970/07/28/archives/new-sears-building-in-chicago-planned-as-the-worlds-tallest.html |access-date=September 7, 2022 |issn=0362-4331}} This would make Sears's new tower the tallest in the world, as measured by roof height, although New York City's under-construction World Trade Center Twin Towers would have a taller antenna. Although the Sears Tower would contain {{convert|4.4|e6ft2}} of space, only about {{convert|3.7|e6ft2}} would be used as offices.

File:Sears Willis Tower.jpg

Work on the building's foundation commenced in August 1970. Contractors excavated the lot to a depth of {{convert|50|ft}}, and they removed {{convert|180000|ft3}} of dirt from the site.{{Cite news |date=April 18, 1971 |title=Build Foundation of Huge Sears Tower |page=D1 |work=Chicago Tribune |id={{proQuest|169075911}}}} By that November, Spencer, White & Prentis Inc. was excavating a trench around the site, measuring {{convert|60|ft}} deep and {{convert|20|by|216|ft}} across. The contractors then built a slurry wall within the trench, made of concrete and reinforced steel.{{Cite news |date=November 22, 1970 |title=New Methods Speed Construction |pages=105 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109124635/new-methods-speed-construction/ |access-date=September 7, 2022}} Workers used steel bracing to prevent the slurry wall from collapsing inward, then used caissons to drill 201 holes into the ground. They also rerouted a sewer that had run underneath Quincy Street, which was to be closed permanently as part of the tower's construction.

The Diesel Construction Company was hired as the Sears Tower's general contractor. Sears, Roebuck & Co. chairman Gordon M. Metcalf installed the building's first steel beam at a ceremony on June 7, 1971.{{Cite news |date=June 8, 1971 |title=Set First Sears Tower Steel |pages=53 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109125056/set-first-sears-tower-steel/ |access-date=September 7, 2022}}{{Cite news |date=June 8, 1971 |title=First Steel in Sears Building |language=en-US |work=The New York Times |url=https://www.nytimes.com/1971/06/08/archives/first-steel-in-sears-building.html |access-date=September 7, 2022 |issn=0362-4331}} The project employed 2,000 workers. To accelerate the building's construction, a concrete plant was built in the building's basement, allowing workers to pour one-third of a concrete floor every day. Contractors built two temporary kitchens on the site for workers, and telephone and loudspeaker systems were installed on every floor to allow workers to communicate. In addition, contractors installed temporary generators that could supply up to {{convert|14000|kW}} simultaneously; during the winter, most of this electricity was used to heat the exposed steel beams on the lowest five floors.{{Cite news |date=October 3, 1971 |title=Sears Tower Uses Unique New Systems |pages=97 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109125194/sears-tower-uses-unique-new-systems/ |access-date=September 7, 2022}}

By late 1971, Chicagoland residents and broadcasters had raised concerns that the new Sears Tower would disrupt television broadcasts.{{Cite news |last=Horton |first=Luci |date=November 25, 1971 |title=Your TV on the Blink? Blame Sears... Tower, That Is! |pages=163 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109139976/your-tv-on-the-blink-blame-sears/ |access-date=September 7, 2022}} According to one estimate, the building would obstruct television signals for 15 percent of Chicagoans and cause "double images" for another 20 percent,{{cite magazine |last=Roth |first=Morry |date=November 24, 1971 |title=Radio-Television: Chicago Group Bids Stations Take Stand Vs. Now Building Sears Tower |magazine=Variety |volume=265 |issue=2 |pages=44 |id={{ProQuest|1014881361}}}} primarily affecting communities to the northwest and southeast. The same year, officials of the village of Skokie, northwest of Chicago, threatened to request an injunction to prevent further construction.{{cite magazine |last=Osbon |first=John |date=August 9, 1971 |title=Tv Ghosts May Haunt New Sears Tower |magazine=Women's Wear Daily |volume=123 |issue=27 |pages=30 |id={{ProQuest|1862362537}}}}{{Cite news |last=Sluis |first=William |date=July 16, 1971 |title=Sears Tower Faces Suit Over TV Effect |page=A13 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109144740/ |access-date=September 7, 2022 |id={{proQuest|169116946}}}} In response to these concerns, Sears started researching methods to reduce the tower's effect on broadcast signals. Variety magazine stated that the Sears Tower did not interfere with broadcasts on its own, since several shorter towers in the Loop also interfered with broadcast signals.{{cite magazine |last=Roth |first=Morry |date=December 29, 1971 |title=Radio-Television: TV Operators In Chi Prefer To Pass Their Own Roebuck, Bounce Back On Group Protesting Tall Sears Tower |magazine=Variety |volume=265 |issue=7 |pages=23 |id={{ProQuest|962900933}}}} Nonetheless, the Illinois Citizens' Committee for Broadcasting filed a formal complaint with the Federal Communications Commission (FCC) in February 1972.{{cite magazine |last=Roth |first=Morry |date=February 23, 1972 |title=Local TV-Radio & Syndication: Chicago Broadcast Group Works Up To 110-Story 19 Of Wrongs' On Sears Tower For Weighing By FCC |magazine=Variety |volume=266 |issue=2 |pages=44 |id={{ProQuest|962940770}}}}{{Cite news |date=February 17, 1972 |title=U. S. Asked to Act in Sears TV Battle |pages=81 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109147175/u-s-asked-to-act-in-sears-tv-battle/ |access-date=September 7, 2022}}

The first lawsuit against the building was filed by the state attorney in neighboring Lake County on March 17, 1972.{{Cite news |last=Philips |first=Richard |date=April 9, 1972 |title=Sears Tower Case May Cloud More than TV |pages=414 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109144843/sears-tower-case-may-cloud-more-than/ |access-date=September 7, 2022}}{{cite magazine |last=Osbon |first=John |date=April 14, 1972 |title=Ghosts Walk, Flak Flies Over Sears' Tower TV |magazine=Women's Wear Daily |volume=124 |issue=74 |pages=18 |id={{ProQuest|1523617607}}}} A second suit was filed on March 28 in Cook County Circuit Court by the villages of Skokie, Northbrook, and Deerfield, Illinois.{{Cite news |last=Phillips |first=Richard |date=April 9, 1972 |title=Sears Tower Case May Cloud More than TV |pages=185 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109147655/sears-tower-case-may-cloud-more-than/ |access-date=September 7, 2022}} Sears filed motions to dismiss the Lake and Cook County lawsuits, which both sought to cap the building at 67 stories. Sears studied the possibility of erecting antennas atop its tower in April 1972,{{Cite news |date=April 8, 1972 |title=TV Antennas Studied for Sears Tower |pages=3 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109147526/tv-antennas-studied-for-sears-tower/ |access-date=September 7, 2022}} and the tower's construction continued, even as decisions on both lawsuits were delayed.{{Cite news |last=Phillips |first=Richard |date=May 7, 1972 |title=Tower Keeps Rising: Sears TV Suits Delayed |pages=40 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109147882/tower-keeps-rising-sears-tv-suits/ |access-date=September 8, 2022}} At the end of the month, the company applied for permission to increase the building's height limit by {{convert|350|ft}} and install a new antenna,{{Cite news |date=April 27, 1972 |title=Cost of Sears Move Million Per Station |page=A13 |work=Chicago Tribune |id={{proQuest|170299578}}}}{{Cite news |date=April 28, 1972 |title=Channel 7 Antenna to Be Atop Sears Tower |pages=2 |work=The Daily Herald |url=https://www.newspapers.com/clip/109146915/channel-7-antenna-to-be-atop-sears-tower/ |access-date=September 7, 2022}} although eight of Chicago's ten television stations criticized the plan.{{cite magazine |date=May 8, 1972 |title=Equipment & Engineering: 8 Chicago TV's reject Sears plan |magazine=Broadcasting |volume=82 |issue=19 |pages=54 |id={{ProQuest|1016866948}}}}{{Cite news |date=April 28, 1972 |title=8 Channels Rap Sears TV Tower Plea |page=1 |work=Chicago Tribune |id={{proQuest|170289375}}}} On May 17, 1972, Judge LaVerne Dickson, Chief of the Lake County Circuit Court, dismissed the suit, saying, "I find nothing that gives television viewers the right to reception without interference."{{Cite news |date=May 18, 1972 |title=Suit Against Sears Tower, TV "Ghosts" Is Dismissed |pages=2 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109147753/suit-against-sears-tower-tv-ghosts/ |access-date=September 7, 2022}} By then, the building had reached the 58th story.{{Cite news |last=Yabush |first=Donald |date=May 25, 1972 |title=Lake County Plans to Appeal Sears Tower TV Ghosts Suit |pages=132 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109146814/lake-county-plans-to-appeal-sears-tower/ |access-date=September 7, 2022}} The Lake County attorney appealed to the Illinois Supreme Court. In his decision on June 12, Judge Charles R. Barrett contended the plaintiffs did not have a right to undistorted television reception.{{Cite news |last=Sneed |first=Michael |date=June 13, 1972 |title=TV Right Denied: Tower Opponents Suffer Setback |pages=3 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109147290/tv-right-denied-tower-opponents-suffer/ |access-date=September 7, 2022}}

Meanwhile, the FCC declined to act on the height dispute on the grounds it did not have jurisdiction.{{Cite news |date=May 27, 1972 |title=TV Disruption by Sears Tower Beyond Our Jurisdiction: FCC |pages=1 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109148173/tv-disruption-by-sears-tower-beyond-our/ |access-date=September 8, 2022}} The FAA approved the antennas atop the tower in June 1972,{{Cite news |last=Phillips |first=Richard |date=June 17, 1972 |title=FAA Approves TV Antennas on Sears Tower |pages=1, [https://www.newspapers.com/clip/109148355/ 2] |work=Chicago Tribune |url=https://www.newspapers.com/clip/109148327/faa-approves-tv-antennas-on-sears/ |access-date=September 8, 2022}}{{Cite news |date=June 17, 1972 |title=FAA Approves TV Antennas for Chicago's Sears Tower |pages=2 |work=The Journal Times |url=https://www.newspapers.com/clip/109148310/faa-approves-tv-antennas-for-chicagos/ |access-date=September 8, 2022}} and the Illinois Supreme Court affirmed the previous rulings by Lake and Cook County circuit courts at the end of the month.{{Cite news|date=July 1, 1972|title=Sears TV Ghost Plea Rejected|pages=95|work=Chicago Tribune|url=https://www.newspapers.com/clip/109178462/sears-tv-ghost-plea-rejected/|access-date=September 8, 2022}} Work was temporarily paused that July due to a labor strike.{{Cite news|date=July 11, 1972|title=Work Still Halted on Sears Tower|pages=22|work=Chicago Tribune|url=https://www.newspapers.com/clip/109178410/work-still-halted-on-sears-tower/|access-date=September 8, 2022}} The next month, Sears formally announced plans for broadcast antennas on the tower's roof,{{cite news|title=Sears Offers Cash to Aid TV|last=Engle|first=Bryce|work=Chicago Tribune|date=August 15, 1972|page=1|id={{proQuest|169200463}}}}{{cite news |id={{ProQuest|133688461}} |title=Sears to Shoo Ghosts By Putting TV Masts Atop Its Skyscraper: Work on Bases May Be Started In December for Move From Chicago John Hancock Sites |date=August 15, 1972 |page=11 |work=The Wall Street Journal|issn=0099-9660}} and the company offered to spend $5 million (equivalent to ${{formatprice|{{inflation|US|5,000,000|1972}}}} in {{inflation/year|US}}){{inflation/fn|US}} to help relocate broadcast stations to the Sears Tower. The United States Court of Appeals for the Seventh Circuit upheld the FCC's decision in September,{{Cite news|date=September 12, 1972|title=FCC Upheld on Sears Tower|pages=3|work=Chicago Tribune|url=https://www.newspapers.com/clip/109178519/fcc-upheld-on-sears-tower/|access-date=September 8, 2022}} and the United States Supreme Court refused to hear an appeal of the Seventh Circuit's decision that November.{{cite magazine |id={{ProQuest|1016888089}} |title=Equipment & Engineering: Supreme Court refuses to stop Sears building |volume=83 |issue=20 |date=November 13, 1972 |pages=41–42 |magazine=Broadcasting}}{{cite news |id={{ProQuest|133690746}} |title=Ruling Allowing Blacks to Collect Damages For Job Bias Left Standing by High Court |date=November 7, 1972 |page=2 |work=The Wall Street Journal|issn=0099-9660}}

In November 1972, the Sears Tower became Chicago's tallest building, surpassing the Standard Oil Building, which had held the record for one month.{{Cite news|date=October 6, 1972|title=Chicago Skyscrapers Onward and Upward|language=en-US|work=The New York Times|url=https://www.nytimes.com/1972/10/06/archives/new_jersey_pages-chicago-skyscrapers-onward-and-upward.html|access-date=September 8, 2022|issn=0362-4331}} At the time, the Sears project employed 1,600 workers in three shifts; one worker had been killed during the project so far.{{cite news |id={{ProQuest|133809828}} |first=Terry P. |last=Brown |title=A Tall Order: How Big Ray Worley, A Screamer and Yeller, Is Building Sears Tower |date=March 22, 1973 |page=1 |work=The Wall Street Journal|issn=0099-9660}} The building's final completion had been delayed significantly due to labor strikes and bad weather. The concrete work had reached the 77th floor, while the steel superstructure had reached the 84th floor; the remainder of the steelwork would be difficult to construct because of high winds at higher altitudes.{{Cite news|date=November 12, 1972|title=Sears Tower Now Tallest in Chicago|pages=101, [https://www.newspapers.com/clip/109179031/ 102]|work=Chicago Tribune|url=https://www.newspapers.com/clip/109178798/sears-tower-now-tallest-in-chicago/|access-date=September 8, 2022}} Local television stations WTTW and WLS-TV were planning to install temporary broadcast antennas atop the tower when the steel frame was completed.{{Cite news|date=November 8, 1972|title=Sears Tower Antennas Eyed '73|pages=51|work=Chicago Tribune|url=https://www.newspapers.com/clip/109179421/sears-tower-antennas-eyed-73/|access-date=September 8, 2022}} The tower's superstructure had reached the 100th floor in February 1973, at which point it was taller than the Empire State Building in New York City.{{Cite news |date=February 24, 1973 |title=Sears Tower work reaches 100th floor |pages=75 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109180911/sears-tower-work-reaches-100th-floor/ |access-date=September 8, 2022}}

The building was topped out on May 3, 1973.{{Cite news |last=Nelson |first=Bryce |date=May 3, 1973 |title=Topping Out of Sears Tower Will Give Chicago the Skyscraper Lead |page=20 |work=Los Angeles Times |id={{proQuest|157279327}}}} The day before the event, the Chicago Tribune{{'s}} editorial board wrote: "Move aside, New York. After tomorrow, when schoolchildren dream of big buildings, they'll no longer think of you and the Empire State Building and the World Trade Center."{{harvnb|Kamin|2001|p=105|ps=.}} The frame was still not technically complete, as three to four stories remained to be built.{{Cite news |date=April 13, 1973 |title=Seek cause of Sears fire that killed 4 |pages=74 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109181933/seek-cause-of-sears-fire-that-killed-4/ |access-date=September 8, 2022}} One week after the ceremony, four workers died after an elevator shaft caught fire.{{Cite news |date=April 12, 1973 |title=Sears Tower Fire Kills 4 Working in Elevator Shaft |language=en-US |work=The New York Times |url=https://www.nytimes.com/1973/04/12/archives/sears-tower-fire-kills-4-working-in-elevator-shaft.html |access-date=September 8, 2022 |issn=0362-4331}} A fifth worker died after falling from the tower in an unrelated incident four days later.{{Cite news |date=April 15, 1973 |title=1 dies in Sears Tower fall; 5th victim in 4 days |page=2 |work=Chicago Tribune |id={{proQuest|169276010}}}} Work was halted again that June due to a labor strike,{{Cite news|last=Strong|first=James|date=June 2, 1973|title=Strike halts work at Sears Tower|pages=19|work=Chicago Tribune|url=https://www.newspapers.com/clip/108216726/strike-halts-work-at-sears-towerjames/|access-date=August 24, 2022}}{{cite news |date=June 4, 1973 |title=Total Work Stoppage Of Construction Due In Chicago Area Today |page=20 |work=The Wall Street Journal |issn=0099-9660 |id={{ProQuest|133810720}}}} and Sears began moving furniture into the building that month.{{Cite news |last=Oppenheim |first=Carol |date=September 9, 1973 |title=Offices for 7,000 employes: Sears begins big move to tower this weekend |pages=40 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109411769/offices-for-7000-employes-sears/ |access-date=September 12, 2022}} The construction cost was about US$150 million,{{Cite web|title=BUILDING BIG: Databank: Sears Tower|url=https://www.pbs.org/wgbh/buildingbig/wonder/structure/sears_tower.html|access-date=September 12, 2022|website=www.pbs.org}} (equivalent to ${{Format price|{{Inflation|US|150,000,000|1973}}}} in {{inflation/year|US}}).{{Inflation-fn|US}} Despite the size of the project, Sears executives said the building could not accommodate Sears' annual shareholder meetings, and the company continued to rent space in other structures.{{cite news |date=May 22, 1973 |title=Sears to Shoo Ghosts By Putting TV Masts Atop Its Skyscraper: Work on Bases May Be Started In December for Move From Chicago John Hancock Sites |page=8 |work=The Wall Street Journal |issn=0099-9660 |id={{ProQuest|133807447}}}}

The first Sears employees began moving into the tower during the weekend of September 9, 1973.{{cite magazine |date=September 11, 1973 |title=In brief...: Weekend moving day to Sears Tower |magazine=Women's Wear Daily |volume=127 |issue=50 |pages=14 |id={{ProQuest|1627236636}}}} Flashing beacons on the building's roof, the first to be installed at any building in Chicago, were activated the same month.{{Cite news |date=September 15, 1973 |title=Big beacons to flash atop Sears Tower |pages=9 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109411685/big-beacons-to-flash-atop-sears-tower/ |access-date=September 12, 2022}} Upon the tower's opening, broadcasters at the John Hancock Center, Chicago's second-tallest building, had to decide whether to relocate to the Sears Tower.{{cite magazine |date=September 19, 1973 |title=Local TV-Radio & Syndication: Sears Tower Gives Ultimatum To Stations On Hancock Switch |magazine=Variety |volume=272 |issue=6 |pages=26 |id={{ProQuest|963306761}}}} Two television stations decided to relocate.{{Cite news |date=October 24, 1973 |title=Two television stations to move to Sears Tower |pages=14 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109412135/two-television-stations-to-move-to/ |access-date=September 12, 2022}} Six other stations remained at the John Hancock Center, citing a study which showed that relocating to the Sears Tower would provide only minimal benefits.{{cite magazine |date=December 5, 1973 |title=Radio-Television: Tall Tower A Searing Issue As Chi TV Stations Plot Moves |magazine=Variety |volume=273 |issue=4 |pages=36, 42 |id={{ProQuest|1032471721}}}} Documents released in late 1973 indicated that the Sears Tower would cause much more interference than either Sears or the television stations had disclosed. WLS-TV moved to the Sears Tower in February 1974,{{Cite news|title=WLS-TV has clearer reception from Sears Tower |work=Chicago Defender|date=February 4, 1974|page=14|id={{proQuest|494041980}}}} followed by WTTW the next month.{{Cite news |date=March 27, 1974 |title=WTTW to begin beaming from Sears Tower |pages=14 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109413166/wttw-to-begin-beaming-from-sears-tower/ |access-date=September 12, 2022}}

By March 1974, three-fourths of the space in the building was occupied; Sears had leased the upper stories to tenants such as Goldman Sachs, Northwest Industries, and Schiff Hardin.{{Cite news |date=March 18, 1974 |title=New Sears Tower leases listed |pages=67 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109413042/new-sears-tower-leases-listed/ |access-date=September 12, 2022}} A mobile sculpture by Alexander Calder was dedicated in the lobby in October 1974.{{Cite news |last=Oppenheim |first=Carol |date=October 26, 1974 |title=A whatchama-Calder sculpture conquers the city |pages=1, [https://www.newspapers.com/clip/47364806/ 4] |work=Chicago Tribune |url=https://www.newspapers.com/clip/109412727/a-whatchama-calder-sculpture-conquers/ |access-date=September 12, 2022}}{{cite book |last1=Drexler |first1=Arthur |url=https://books.google.com/books?id=N6JNEAAAQBAJ |title=SOM: Architecture of Skidmore, Owings & Merrill, 1963-1973 |last2=Menges |first2=Axel |publisher=Monacelli Press |year=2009 |isbn=978-1-58093-221-9 |page=170}} Sears' optimistic growth projections were not realized; instead, in late 1974, the company fired 500 workers, about seven percent of the 7,000 Sears employees that worked in the tower.{{cite magazine |last=Osbon |first=John |date=October 30, 1974 |title=Sears in process of firing 500 at Tower in Chicago |magazine=Women's Wear Daily |volume=129 |issue=87 |pages=1, 22 |id={{ProQuest|1627541851}}}} Competition beyond its traditional rivals such as Montgomery Ward arose from emerging retail giants including Kmart, Kohl's, and Walmart. As a result of a surplus of office space that emerged in the 1980s, the tower did not draw as many tenants as projected and so stood half-vacant for a decade.

File:6 102778 Sears Tower.jpg

In February 1984, Sears announced that it would renovate the building to attract visitors to the lower floors.{{Cite news |date=February 1, 1984 |title=Sears Tower makes dramatic new entrance |pages=31 |work=Chicago Tribune |url=https://www.newspapers.com/clip/108282797/sears-tower-makes-dramatic-new-entrance/ |access-date=August 25, 2022}}{{Cite news |date=February 5, 1984 |title=Sears Tower, world's tallest, to get face-lift |pages=44 |work=The Dispatch |url=https://www.newspapers.com/clip/108282078/sears-tower-worlds-tallest-to-get/ |access-date=August 25, 2022}} At the time, 6,500 Sears employees occupied more than half of the building,{{Cite news |date=September 15, 1985 |title=Sears' Tower is still world's tallest |pages=42 |work=The Dispatch |url=https://www.newspapers.com/clip/108282656/sears-tower-is-still-worlds-tallest/ |access-date=August 25, 2022}} taking up the lowest 48 stories. The remainder of the tower was occupied by 5,500 employees from about 70 companies. As part of the project, the main entrance was covered with a four-story glass dome, and the first four stories were converted into a shopping atrium. In addition, a visitor center for the building's Skydeck was constructed. The renovations, designed by SOM, were completed in mid-1985. Paul Gapp of the Chicago Tribune wrote that SOM had "scaled the new entrance skillfully, in keeping with the main building's height" and that the new atrium "relieves the formerly cramped feeling from just inside the Franklin entrance".{{Cite news |last=Gapp |first=Paul |date=November 17, 1985 |title=Sears Tower's need for changes shows the dangers of thinking too big |pages=321 |work=Chicago Tribune |url=https://www.newspapers.com/clip/108282527/sears-towers-need-for-changes-shows/ |access-date=August 25, 2022}}

Sears announced in 1988 that it would sell the tower and relocate its merchandising division from the lower half of the building.{{Cite news |last=Ziemba |first=Stanley |date=November 6, 1988 |title=Sears executives face a towering selling job |pages=1, [https://www.newspapers.com/clip/108283334/ 30] |work=Chicago Tribune |url=https://www.newspapers.com/clip/108283288/sears-executives-face-a-towering/ |access-date=August 25, 2022}} The company wanted to earn at least $1 billion from the sale of the Sears Tower, so it offered multiple concessions to potential buyers, including a guarantee that Sears would continue to pay rent on the lower half of the building until tenants were found for these stories.{{Cite news |date=April 4, 1989 |title=Sears offering tower concessions |pages=22 |work=The Dispatch |url=https://www.newspapers.com/clip/108283695/sears-offering-tower-concessions/ |access-date=August 25, 2022}} Four large firms were negotiating to buy the tower by July 1989.{{Cite news |last=Ziemba |first=Stanley |date=June 23, 1989 |title=Sears pushing $1 billion-plus bid for Tower |pages=41, [https://www.newspapers.com/clip/108283412/ 46] |work=Chicago Tribune |url=https://www.newspapers.com/clip/108283395/sears-pushing-1-billion-plus-bid-for/ |access-date=August 25, 2022}} The company had difficulties finding a buyer, in part because the lower stories were too large for many potential tenants.{{Cite news |last=Ziemba |first=Stanley |date=November 5, 1989 |title=Sears faces tough sell leasing Tower office space |pages=135 |work=Chicago Tribune |url=https://www.newspapers.com/clip/108283103/sears-faces-tough-sell-leasing-tower/ |access-date=August 25, 2022}} Sears nearly sold the tower to Canadian company Olympia & York, but the deal was canceled in September 1989 because the two firms could not agree on who would pay the property taxes.{{Cite news |last=Ziemba |first=Stanley |date=September 16, 1989 |title=Sears Tower sale to Olympia & York may be dead |pages=21, [https://www.newspapers.com/clip/108283549/ 23] |work=Chicago Tribune |url=https://www.newspapers.com/clip/108283510/sears-tower-sale-to-olympia-york-may/ |access-date=August 25, 2022}} In November 1989, Sears decided to instead refinance the building.{{cite web |last=Ziemba |first=Stanley |date=November 16, 1989 |title=Sears Plans to Refinance, Keep Tower |url=https://www.chicagotribune.com/news/ct-xpm-1989-11-16-8903100339-story.html |access-date=August 24, 2022 |website=Chicago Tribune}} The next year, Sears took out a mortgage loan on the tower for $850 million from MetLife and AEW Capital Management, with MetLife as the holder of the mortgage note; the loan would mature in 2005.

In 1990, the law firm of Keck, Mahin & Cate decided to move into a development that would become 77 West Wacker Drive, rebuffing Sears' attempts to entice the firm to stay.{{Cite web|date=November 2, 2012|title=77 W. Wacker ready to go – Chicago Sun-Times |url=http://www.highbeam.com/doc/1P2-3988744.html|archive-url=https://web.archive.org/web/20121102130617/http://www.highbeam.com/doc/1P2-3988744.html|url-status=dead|archive-date=November 2, 2012|access-date=September 12, 2022}} Just two years later, Sears began moving its own offices out of the building{{Cite web|title=Willis who? Sears Tower gets new name|url=https://www.nbcnews.com/id/wbna31945093|access-date=November 10, 2021|website=NBC News|date=July 16, 2009 |language=en}} to a new campus in Hoffman Estates, Illinois, which was completed in 1995.{{Cite news|url=https://www.valuewalk.com/wp-content/uploads/2015/11/Sears_Tower.pdf|title=A Case Study of the Development, Re-financing and Sale of North America's Tallest Building|work=tribunedigital-chicagotribune|access-date=February 9, 2018|language=en|archive-date=November 9, 2021|archive-url=https://web.archive.org/web/20211109041350/https://www.valuewalk.com/|url-status=dead}} As the maturation of the mortgage approached, Sears renegotiated the loan in 1994. The negotiations resulted in an agreement where Sears would no longer be liable for the $850 million loan, although it would only nominally own the building, while AEW and MetLife effectively had total control. As part of the 1994 agreement, AEW and MetLife would be able to take official ownership of the building in 2003. In 1997, Toronto-based TrizecHahn, at the time the lessee of the CN Tower, acquired AEW's holdings in the building for $110 million, assuming $4 million in liabilities and a $734 million mortgage.{{Cite news |last=Vinocur |first=Barry | title=A Look at the Finer Points of the Sears Tower Sale | url=https://www.barrons.com/articles/SB881366507903480500 | work=Barron's | date=December 8, 1997}}{{Cite web|date=December 14, 2001|title=Sears Tower: Headlines|url=http://www.searstower.org/news.html#A0203302202|archive-url=https://web.archive.org/web/20011214200520/http://www.searstower.org/news.html#A0203302202|url-status=dead|archive-date=December 14, 2001|access-date=September 12, 2022}}

Trizec had projected that the Sears Tower would quickly reach a value of $1 billion. These projections were not met, with the tower facing the same vacancy and other problems it saw under Sears, although Trizec made somewhat successful efforts to attract new tenants. Following the September 11 attacks, two of the largest tenants, Goldman Sachs and Merrill Lynch, immediately announced plans for vacating 300,000 ft² of space. In 2003, Trizec sold its holdings of the tower to MetLife for $9 million.{{Cite web|date=December 14, 2001|title=Sears Tower: Headlines|url=http://www.searstower.org/news.html#A1732723553|archive-url=https://web.archive.org/web/20011214200520/http://www.searstower.org/news.html#A1732723553|url-status=dead|archive-date=December 14, 2001|access-date=September 12, 2022}}

In March 2004, MetLife announced that it would sell the building to a group of investors,{{cite web | title=MetLife Selling Chicago's Sears Tower | website=AP NEWS | date=March 12, 2004 | url=https://apnews.com/article/ee67fc8300904659abe80fd65411caee | access-date=August 24, 2022}}{{cite web | last=Corfman | first=Thomas A. | title=Group to buy Sears Tower for $835 million | website=Chicago Tribune | date=March 12, 2004 | url=https://www.chicagotribune.com/news/ct-xpm-2004-03-12-0403120203-story.html | access-date=August 24, 2022}} including Joseph Chetrit, Joseph Moinian, Lloyd Goldman, Joseph Cayre, and Jeffrey Feil of New York, as well as American Landmark Properties of Skokie, Illinois.{{Cite web|date=May 1, 2004|title=Biz Briefs|work=Chicago Sun-Times|url=http://www.highbeam.com/doc/1P2-1527288.html|archive-url=https://web.archive.org/web/20121026073212/http://www.highbeam.com/doc/1P2-1527288.html|url-status=dead|archive-date=October 26, 2012|access-date=September 12, 2022}} The quoted price was $840 million, with $825 million held in a mortgage.{{Cite web|date=April 30, 2004|title=Biz Briefs|work=Chicago Sun-Times|url=http://www.highbeam.com/doc/1G1-118314848.html|archive-url=https://web.archive.org/web/20121026073220/http://www.highbeam.com/doc/1G1-118314848.html|url-status=dead|archive-date=October 26, 2012|access-date=September 12, 2022}} Two years later, in February 2007, the Sears Tower's owners obtained a $780 million loan from UBS.{{cite web | title=Sears Tower's owners complete refinancing | website=Crain's Chicago Business | date=February 1, 2007 | url=https://www.chicagobusiness.com/article/20070201/CRED03/200023711/sears-tower-s-owners-complete-refinancing | access-date=August 24, 2022}} At the time, UBS valued the tower at $1.2 billion.{{cite web | last=Diesenhouse | first=Susan | title=Sears Tower: Tall bill to fill | website=Chicago Tribune | date=August 12, 2007 | url=https://www.chicagotribune.com/news/ct-xpm-2007-08-12-0708110027-story.html | access-date=August 24, 2022}}

File:Willis Tower night 2.jpg

Since 2007, the owners had considered plans for the construction of a hotel on the north side of Jackson Boulevard, between Wacker Drive and Franklin Street, close to the entrance of the observation deck, above the tower's underground parking garage. According to the tower's owners, the second building was considered in the original design. The plan was eventually cancelled as city zoning did not permit construction of such a tall building in that location.{{Cite web|first=David|last=Roeder|title=Tall order for Tower?; Sears Tower owners to press city for zoning change, subsidy to add 2nd building as part of mega-million-dollar project next to landmark|work=Chicago Sun-Times|date=October 12, 2007|url=http://www.highbeam.com/doc/1P2-8884264.html|archive-url=https://web.archive.org/web/20121102173519/http://www.highbeam.com/doc/1P2-8884264.html|url-status=dead|archive-date=November 2, 2012|access-date=September 12, 2022}} In February 2009, the owners announced they were considering a plan to paint the structure silver, an idea that was later abandoned. It was hoped that a new, silver, paint-job would "rebrand" the building and highlight its advances in energy efficiency for an estimated cost of $50 million.[http://www.suntimes.com/business/roeder/1448083,CST-FIN-roeder25.article "Sears Tower in silver?"], Chicago Sun-Times, February 25, 2009 {{webarchive |url=https://web.archive.org/web/20100217125635/http://www.suntimes.com/business/roeder/1448083,CST-FIN-roeder25.article |date=February 17, 2010 }}

Although Sears' naming rights expired in 2003, the building continued to be called the Sears Tower for several years, despite multiple changes in ownership. In March 2009, London-based insurance broker Willis Group Holdings agreed to lease a portion of the building and obtained the naming rights.{{cite news|url=http://archives.chicagotribune.com/2009/mar/12/business/chi-biz-sears-tower-name-change-willis-march12 |title=Sears Tower name to change to Willis Tower |date=March 12, 2009 |work=Chicago Tribune |access-date=May 1, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090419220724/http://archives.chicagotribune.com/2009/mar/12/business/chi-biz-sears-tower-name-change-willis-march12 |archive-date=April 19, 2009 }}{{Cite news|last=Cullotta|first=Karen Ann|date=March 13, 2009|title=Illinois: New Name for the Sears Tower|language=en-US|work=The New York Times|url=https://www.nytimes.com/2009/03/13/us/13brfs-NEWNAMEFORTH_BRF.html|access-date=September 12, 2022|issn=0362-4331}} On July 16, 2009, the building was officially renamed the Willis Tower.{{cite web | title=Willis who? Sears Tower gets new name | website=NBC News | date=July 16, 2009 | url=https://www.nbcnews.com/id/wbna31945093 | access-date=September 12, 2022}} By 2011, the building's owners were considering selling a partial ownership stake, or even the entire building, to an investor.{{cite web | last=Jonas | first=Ilaina | title=Exclusive: Owners of former Sears Tower seek investor | website=U.S. | date=June 1, 2011 | url=https://www.reuters.com/article/us-searstower-idUSTRE7506BJ20110601 | access-date=August 24, 2022}} The next year, United Airlines announced it would move its corporate headquarters from 77 West Wacker Drive to the Willis Tower.

By March 2015, the Willis Tower was being marketed at a price of $1.5 billion.{{cite web | title=Willis Tower Up For Sale | website=CBS News | date=March 5, 2015 | url=https://www.cbsnews.com/chicago/news/willis-tower-up-for-sale/ | access-date=August 24, 2022}} The same month, the Blackstone Group purchased the tower for a reported $1.3 billion, the highest price ever paid for a property in the U.S. outside of New York City.{{cite web | title=Blackstone seals deal to buy Willis Tower | website=Crain's Chicago Business | date=March 15, 2015 | url=https://www.chicagobusiness.com/article/20150316/CRED03/150319854/willis-tower-sale-to-blackstone-breaks-chicago-record | access-date=August 24, 2022}}{{cite web | last=Harris | first=Melissa | title=Willis Tower to be sold for $1.3 billion to Blackstone Group | website=Chicago Tribune | date=March 15, 2015 | url=https://www.chicagotribune.com/business/ct-willis-tower-being-sold-biz-20150315-story.html | access-date=August 24, 2022}} Blackstone announced a $500 million renovation in January 2017, which would include the construction of the Catalog, a six-story commercial complex, replacing a plaza on Jackson Boulevard and the entrance on Wacker Drive.{{Cite news|url=https://chicago.suntimes.com/business/willis-tower-in-line-for-500-million-facelift/|title=Willis Tower in line for a $500 million facelift|work=Chicago Sun-Times|access-date=October 3, 2018|language=en}}{{cite web | title=Willis Tower owner unveils $500 million redevelopment vision | website=Crain's Chicago Business | date=January 31, 2017 | url=https://www.chicagobusiness.com/article/20170201/CRED03/170209976/willis-tower-owner-unveils-500-million-redevelopment-vision | access-date=August 24, 2022}} Architectural firm Gensler designed the renovation.{{cite web |last=Gauer |first=James |date=May 1, 2022 |title=Willis Tower Transformation by Gensler |url=https://www.architecturalrecord.com/articles/15633-willis-tower-transformation-by-gensler |access-date=September 7, 2022 |website=Architectural Record}} A rooftop terrace was built atop the Catalog, and the building's HVAC systems were overhauled. Most of the building's elevators, excluding those that served the Skydeck, were also renovated for the first time in the tower's history. The new elevators would be faster than the original elevators and would use 35 percent less energy.{{cite web |last=Koziarz |first=Jay |date=May 8, 2018 |title=Willis Tower is getting faster, greener elevators |url=https://chicago.curbed.com/2018/5/8/17328682/construction-willis-tower-elevator-speed |access-date=September 7, 2022 |website=Curbed Chicago}}{{cite web |last1=Ori |first1=Ryan |last2=Brinson |first2=Jemal R. |date=May 4, 2018 |title=Willis Tower getting new elevators: Here are the ups and downs |url=https://www.chicagotribune.com/business/ct-biz-willis-tower-elevators-numbers-htmlstory.html |access-date=September 7, 2022 |website=Chicago Tribune}} The building's owners installed artwork by Olafur Eliasson, Jacob Hashimoto, and other artists.{{cite web |last=Rogal |first=Brian J. |date=May 23, 2022 |title=Willis Tower owners wrap up $500 million makeover that includes new retail hub, enhanced amenities |url=https://www.chicagotribune.com/business/ct-biz-willis-tower-revamp-20220523-hascw3jnzbh4pgrmwpw77fu2wm-story.html |access-date=September 7, 2022 |website=Chicago Tribune}}

To fund these improvements, in February 2017, Blackstone obtained a $1 billion loan from a group of banks including Goldman Sachs. The new loan replaced $750 million of CMBS debt that was maturing.{{cite web | title=Willis Tower's new loan: $1 billion | website=Crain's Chicago Business | date=February 7, 2017 | url=https://www.chicagobusiness.com/article/20170208/CRED03/170209843/willis-tower-s-new-loan-1-billion | access-date=August 24, 2022}} The following year, because of the increasing costs of the renovation,{{cite web | last=Sudo | first=Chuck | title=Blackstone Group Refinances Willis Tower Debt, As Redevelopment Costs Climb | website=Bisnow | date=April 3, 2018 | url=https://www.bisnow.com/chicago/news/office/blackstone-group-refinances-willis-tower-debt-as-redevelopment-costs-climb-86897 | access-date=August 24, 2022}} Blackstone received a new $1.3 billion loan from Deutsche Bank and Barclays.{{Cite web|last=Pilgrim|first=Lexi|date=April 3, 2018|title=Blackstone takes out record $1.3B+ refi for Willis Tower|url=https://therealdeal.com/chicago/2018/04/03/blackstone-takes-out-record-1-3b-refi-for-willis-tower/|access-date=August 24, 2022|website=The Real Deal Chicago|language=en-US}}{{cite web | title=Blackstone piles on more debt at Willis Tower | website=Crain's Chicago Business | date=April 2, 2018 | url=https://www.chicagobusiness.com/article/20180403/CRED03/180409983/willis-tower-owner-blackstone-refinances-skyscraper-with-305-million-in-new-debt | access-date=August 24, 2022}} The Wacker Drive "Lunchbox" entrance was demolished in early 2018 to make way for the Catalog.{{cite web |last=Koziarz |first=Jay |date=April 6, 2018 |title=Willis Tower says goodbye to its "lunchbox" pavilion |url=https://chicago.curbed.com/2018/4/6/17206014/willis-tower-construction-lunchbox-globe |access-date=September 7, 2022 |website=Curbed Chicago}} A steel globe next to the entrance, manufactured by the Poblocki Sign Company and installed in 2010, was relocated to Elmhurst, Illinois.{{cite web |date=February 15, 2018 |title=Willis Tower's Iconic Globe Sculpture Has A New Home In The Suburbs |url=https://www.bisnow.com/chicago/news/construction-development/willis-towers-iconic-globe-sculpture-has-a-new-home-in-the-suburbs-85060 |access-date=September 7, 2022 |website=Bisnow}} A {{convert|40000|ft2|adj=on}} private club on the 66th and 67th stories opened in June 2018. The club included a restaurant named Craftsman and a lounge named Frame, both of which exclusively served the tower's tenants, as well as a public restaurant known as the East Room.{{cite web |last=Selvam |first=Ashok |date=June 28, 2018 |title=Willis Tower Club Debuts a New 66th-Floor Restaurant and Lounge |url=https://chicago.eater.com/2018/6/28/17516094/willis-tower-lounge-restaurant-frame-craftsman-east-room-metropolitan-club |access-date=September 7, 2022 |website=Eater Chicago}}{{cite web |last=Koziarz |first=Jay |date=November 16, 2017 |title=Big changes on tap for Willis Tower's Metropolitan Club |url=https://chicago.curbed.com/2017/11/16/16666100/willis-tower-metropolitan-club-renovations |access-date=September 7, 2022 |website=Curbed Chicago}} That September, Urbanspace announced that it would operate a food hall on the lower stories.{{cite web |date=September 6, 2018 |title=Willis Tower getting its first food hall |url=https://www.chicagobusiness.com/commercial-real-estate/willis-tower-getting-its-first-food-hall |access-date=September 7, 2022 |website=Crain's Chicago Business}}{{cite web |last=Selvam |first=Ashok |date=September 7, 2018 |title=A Food Hall is Coming to Willis Tower |url=https://chicago.eater.com/2018/9/7/17831704/willis-tower-food-hall-chicago-loop-urbanspace |access-date=September 7, 2022 |website=Eater Chicago}}

In 2020, insurance company Aon had proposed acquiring Willis Towers Watson (which had succeeded the Willis Group as the building's owner),{{cite web | title=Aon to Buy Willis Towers Watson | website=Insurance Journal | date=March 9, 2020 | url=https://www.insurancejournal.com/news/international/2020/03/09/560582.htm | access-date=September 12, 2022}}{{Cite news|last=Dummett|first=Ben|date=March 9, 2020|title=Insurance Broker Aon Strikes Year's Biggest M&A Deal on Tumultuous Markets Day|language=en-US|work=The Wall Street Journal|url=https://www.wsj.com/articles/aon-to-merge-with-willis-towers-watson-in-all-stock-deal-valued-at-30-billion-11583758247|access-date=September 12, 2022|issn=0099-9660}} prompting speculation that the building could be renamed again.{{cite web | last=Smith | first=Ryan | title=Willis Tower Name Changes, Ranked by Likelihood | website=Chicago Magazine | date=April 2020 | url=https://www.chicagomag.com/city-life/April-2020/Willis-Tower-Naming-Power-Rankings/ | access-date=September 12, 2022}} The planned merger was canceled in 2021 following an antitrust lawsuit from the United States Department of Justice.{{cite web | title=Insurance brokers Aon and Willis Towers Watson scrap their $30 billion merger | website=CNBC | date=July 26, 2021 | url=https://www.cnbc.com/2021/07/26/insurance-brokers-aon-and-willis-towers-watson-scrap-their-30-billion-merger.html | access-date=September 12, 2022}} The building's renovation was completed in May 2022.{{cite web |date=May 24, 2022 |title=Willis Tower unveils $500 million makeover with updates to the Skydeck |url=https://www.cbsnews.com/chicago/news/willis-tower-unveils-500-million-makeover-with-updates-to-the-skydeck/ |access-date=August 24, 2022 |website=CBS News}}{{Cite web |last=Hourie |first=Ilya |date=May 24, 2022 |title=Blackstone Unveils $500M Renovation Of Willis Tower |url=https://therealdeal.com/chicago/2022/05/24/blackstone-unveils-500m-rto-bet-on-chicagos-willis-tower/ |access-date=August 24, 2022 |website=The Real Deal Chicago |language=en-US}} At the time, although the Willis Tower was nearly 85 percent leased, the number of tenants and visitors entering the building had decreased significantly since 2019, in part because of the COVID-19 pandemic in Chicago. In April 2023, The New York Times reported that Blackstone had written down the value of its investment in the tower by $119 million.{{Cite news|last1=Goldstein|first1=Matthew|last2=Creswell|first2=Julie|last3=Eavis|first3=Peter|date=April 27, 2023|title=Stress Builds as Office Building Owners and Lenders Haggle Over Debt|language=en-US|work=The New York Times|url=https://www.nytimes.com/2023/04/27/business/economy/office-buildings-banks-economy.html|access-date=May 4, 2023|issn=0362-4331}}

In June 2006, seven men were arrested by the FBI and charged with plotting to destroy the tower. Deputy FBI Director John Pistole described their plot as "more aspirational than operational".{{Cite news|last1=Shane|first1=Scott|last2=Zarate|first2=Andrea|date=June 24, 2006|title=F.B.I. Killed Plot in Talking Stage, a Top Aide Says|language=en-US|work=The New York Times|url=https://www.nytimes.com/2006/06/24/us/24terror.html|access-date=September 12, 2022|issn=0362-4331}}{{Cite news|date=June 23, 2006|title=Seven charged over 'Chicago plot'|language=en-GB|url=http://news.bbc.co.uk/2/hi/americas/5110342.stm|access-date=September 12, 2022}} The case went to court in October 2007.{{Cite news|date=October 3, 2007|title=Sears Tower "plot" trial begins|language=en-GB|url=http://news.bbc.co.uk/2/hi/americas/7025316.stm|access-date=September 12, 2022}} After three trials, five of the suspects were convicted and two acquitted.{{Cite news|date=May 12, 2009|title=Five guilty in Chicago bomb plot|language=en-GB|url=http://news.bbc.co.uk/2/hi/americas/8046984.stm|access-date=September 12, 2022}} The alleged leader of the group, Narseal Batiste, was sentenced to {{frac|13|1|2}} years in prison.{{Cite news|date=November 20, 2009|title=Sears Tower plot leader is jailed|language=en-GB|url=http://news.bbc.co.uk/2/hi/americas/8371671.stm|access-date=September 12, 2022}} In response to the perceived threat of an attack, the building's largest tenant at this time, Ernst & Young, moved to North Wacker Drive in early 2009.{{cite web|url=http://www.thechicago77.com/2009/01/sears-tower-to-lose-largest-tenant/|title=Sears Tower to Lose Largest Tenant - The Chicago 77|website=www.thechicago77.com|date=January 9, 2009|access-date=October 3, 2018}}

In May 2020, heavy rains caused three of the basement levels to flood, knocking out power to the building. This also resulted in many TV and radio stations going off the air.{{Cite news|url=https://www.robertfeder.com/2020/05/20/flooding-willis-tower-knocks-tv-radio-signals-off-air/|title=Flooding at Willis Tower knocks TV, radio signals off the air|date=May 20, 2020}}

{{Stack|File:Willis Tower tube structure.svg of Willis Tower with simplified floor plans]]}}

The Willis Tower was designed by architect Bruce Graham and structural engineer Fazlur Rahman Khan of Skidmore, Owings and Merrill.{{harvnb|Pridmore|Larson|2018|ps=.|p=181}} Graham and Khan designed the building as nine square "tubes", clustered in a 3×3 matrix forming a square base with {{convert|225|ft|m|adj=on}} sides. The building's rentable area is {{convert|3810000|ft2|m2|-2|abbr=on}}.{{Cite web |title=Willis Tower |url=https://www.som.com/projects/willis-tower-formerly-sears-tower/ |access-date=2024-07-22 |website=SOM |language=en-US}} The structure was intended to accommodate 16,500 employees.{{cite news |last=Hoyt |first=Monty |date=June 22, 1973 |title=Sears Tower, world's tallest, may also be world's safest: No alternative to safety "Bundled tube" design |page=12 |work=The Christian Science Monitor |id={{ProQuest|511514170}}}}

Each of the "tubes" is a column-free module measuring {{convert|75|by|75|ft}},{{cite web |date=September 2, 2007 |title=Sears Tower |url=http://www.tallestbuildingintheworld.com/building_id_5_Sears+Tower.php |url-status=dead |archive-url=https://web.archive.org/web/20090226193756/http://www.tallestbuildingintheworld.com/building_id_5_Sears+Tower.php |archive-date=February 26, 2009 |access-date=September 14, 2009 |work=TallestBuildingintheWorld.com}} which set back at different stories. There are setbacks at the 50th, 66th, and 90th floors.{{cite book |last1=Žaknić |first1=Ivan |title=100 of the world's tallest buildings |last2=Smith |first2=Matthew |last3=Rice |first3=Dolores B. |author4=Council on Tall Buildings and Urban Habitat |date=1998 |publisher=Gingko Press |isbn=3-927258-60-1 |page=207 |oclc=40110184}} The lowest 50 stories contain nine tubes and cover {{convert|52000|ft2}} each. The northwest and southeast tubes terminate at the 50th floor. The 51st through 66th floors each span {{convert|41420|ft2}}, above which the northeast and southwest tubes end. From the 67th to 90th floors, each story is shaped like a cross, covering {{convert|30170|ft2}}. The north, east, and south tubes end at the 90th floor; the remaining west and center tubes reach 108 floors, with an area of {{convert|12283|ft2}} on each of the top stories.

File:FR khan sculputure at Sears tower.jpg, considered the father of tubular designs, at the Willis Tower. Khan is known for making important advancements in skyscraper engineering.]]

The Sears Tower was the first building to use this innovative design. It was both structurally efficient and economic: at 1,450 feet, it provided more space and rose higher than the Empire State Building and cost much less per unit area.{{cite book |author=National Academy of Engineering |url=https://books.google.com/books?id=vD0rAAAAYAAJ |title=Memorial Tributes |publisher=National Academies |year=1979 |isbn=9780309034821 |id=NAP:14723}} The system would prove highly influential in skyscraper construction and has been used in most supertall buildings since, including the world's current tallest building, the Burj Khalifa.{{cite news |title=Burj Dubai: The new pinnacle of vanity |newspaper=Telegraph |url=https://www.telegraph.co.uk/news/worldnews/middleeast/dubai/6934603/Burj-Dubai-The-new-pinnacle-of-vanity.html |url-status=live |url-access=subscription |access-date=February 25, 2014 |archive-url=https://ghostarchive.org/archive/20220111/https://www.telegraph.co.uk/news/worldnews/middleeast/dubai/6934603/Burj-Dubai-The-new-pinnacle-of-vanity.html |archive-date=January 11, 2022}}{{cbignore}}{{cite news |title=Top 10 world's tallest steel buildings |newspaper=Construction Week Online |date=September 27, 2010 |url=http://www.constructionweekonline.com/article-9180-top-10-worlds-tallest-steel-buildings/1/print/ |access-date=February 25, 2014 |publisher=Constructionweekonline.com}} In February 1982, two television antennas were added to the structure, increasing its total height to {{convert|1707|ft|m|1}}. The western antenna was later extended, bringing the overall height to {{convert|1729|ft|m|1}} on June 5, 2000, to improve reception of local NBC station WMAQ-TV.

The perimeter of the Willis Tower contains columns that are spaced {{convert|15|ft}} apart on their centers. The facade is made of anodized aluminum and black glass. Alcoa manufactured {{convert|4|e6lb}} of aluminum sheeting for the building's facade.{{Cite news |date=August 9, 1971 |title=Alcoa to Supply Sears Tower Aluminum Sheet |pages=68 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109143707/alcoa-to-supply-sears-tower-aluminum/ |access-date=September 7, 2022}} Black bands appear on the tower around the 29th–32nd, 64th–65th, 88th–89th, and 104th–108th floors. These elements are louvers to ventilate the building's environmental support systems and obscure its belted trusses.The Times-News, February 15, 1975 The rest of the facade is made of 16,000 rectangular windows.{{Cite news |last=Nagelberg |first=Alvin |date=June 24, 1973 |title=Going up:: a fantastic elevator voyage The Sears Tower Almanac 14 Sears Escalators link the 33d and 34th floors |page=I14 |work=Chicago Tribune |id={{proQuest|170442312}}}}{{cite news |date=June 2, 1973 |title=Sears Tower Now Tallest In Nation |page=E12 |work=The Washington Post, Times Herald |issn=0190-8286 |id={{ProQuest|148412303}}}} all of which measure {{convert|5|by|8|ft}} and are tinted with bronze.

Outside the building, there was originally a {{convert|80000|ft2|adj=on}} plaza made of pink granite. In the late 2010s, a three-level wing was built along the western and southern sides of the tower replacing the plaza. The roof garden above the annex spans {{convert|30000|ft2}}.{{cite web |date=October 22, 2020 |title=Final Touches Remain for Catalog, Willis Tower's New Podium in The Loop |url=https://chicagoyimby.com/2020/10/final-touches-remain-for-catalog-willis-towers-new-podium-in-the-loop.html |access-date=September 7, 2022 |website=Chicago YIMBY}} The annex contains a facade of black steel and aluminum, similar to in the original building. The Jackson Boulevard facade of the annex contains an artwork by Olafur Eliasson, entitled Atmospheric wave wall.{{cite web |title=Art of the Neighborhood New |url=https://www.willistower.com/artoftheneighborhood |access-date=September 7, 2022 |website=Willis Tower}}{{cite web |last=Li |first=Jennifer S. |date=January 13, 2021 |title=Olafur Eliasson's New Chicago Art Installation Captures Shifting Sunlight and a Changing Climate |url=https://www.architecturaldigest.com/story/olafur-eliassons-chicago-new-art-installation-captures-shifting-sunlight-and-a-changing-climate |access-date=September 7, 2022 |website=Architectural Digest}} The work, measuring {{convert|30|by|60|ft}} across, comprises almost 2,000 blue-and-green steel tiles, which are decorated with hexagonal motifs.{{cite web |last=Neira |first=Juliana |date=January 20, 2021 |title=Olafur Eliasson Installs 1,963 Dynamic Metal Tiles at Chicago's Willis Tower |url=https://www.designboom.com/art/olafur-eliasson-atmospheric-wave-wall-willis-tower-chicago-01-21-2021/ |access-date=September 7, 2022 |website=designboom}} The wall is backlit at night.

The interior includes {{convert|74000|ST|LT t}} of steel, {{convert|4|e6lb}} of aluminum, and {{convert|101|acre|ft2 m2}} of concrete flooring. The building contains diagonal columns only on the two stories immediately below each of the setbacks, thus reducing shear stress. The interior of the building could not contain diagonal beams, since these would have obstructed the connections between each of the "tubes". Therefore, the columns and the horizontal beams on each story are connected by rigid joints. The superstructure was designed to withstand wind gusts of {{convert|130|mph}}, which on average would occur once every hundred years. According to the Chicago Tribune, the top of the building would be able to bend by as much as {{convert|7|in}}, returning to its normal position within 7.2 seconds.

The Willis Tower's basement extends {{Convert|50|ft}} deep, resting on a {{convert|5|ft|m|-thick|adj=mid}} concrete slab. The ground directly beneath the building was largely made of clay; the underlying layer of limestone was as much as {{Convert|100|ft}} beneath ground level. As a result, the foundation was excavated using 201 caissons, of which 114 reached the underlying limestone. The caissons created holes that measured up to {{convert|10|ft}} across. Some holes at the northwestern and northeastern corners of the site filled up with groundwater and had to be drained. Workers next placed steel tubes into the holes, then poured concrete around the tubes.

During the Sears Tower's construction, SOM and Chicago government officials considered adding "smoke free and fire free" areas to the building, as well as a complete sprinkler system serving all floors. Neither of these features had previously been used in a structure in Chicago.{{Cite news |last=Zahour |first=Frank |date=January 3, 1971 |title=City Planners Consider Pioneer Ideas for Including Fire Safety in Sears Tower |pages=34 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109143307/city-planners-consider-pioneer-ideas/ |access-date=September 7, 2022}} Even though regulations did not require a fire sprinkler system, the building was equipped with one from the beginning. There are around 40,000 sprinkler heads in the building, installed at a cost of $4 million. When it was completed, the Sears Tower was heated electrically, unlike older structures that used gas heating.{{Cite news |last=Nagelberg |first=Alvin |date=January 27, 1971 |title=Sears Tower Goes Electric; Standard Turns to Gas |pages=53 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109146209/sears-tower-goes-electric-standard/ |access-date=September 7, 2022}} It included 145,000 light fixtures and a cooling system capable of 17,000 tons of refrigeration. Furthermore, the tower contained fire-suppression and communications systems for emergency use, which were powered by diesel generators.{{Cite news |date=March 11, 1973 |title=Sears Tower betters code |pages=551 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109180857/sears-tower-betters-code/ |access-date=September 8, 2022}} If there was a fire in one section of the building, the building's smoke-detection system would close off the fresh-air intake openings in that section, discharging smoke outdoors.

Fifteen above-ground stories, as well as three of the basement levels, contain mechanical equipment. Above the Skydeck on the 103rd floor is a seven-story mechanical penthouse.

The Sears Tower was planned with 103 elevators, including 14 double-deck elevators.{{Cite news |date=October 11, 1970 |title=Sears Tower: What the Pedestrian Will See |page=C1 |work=Chicago Tribune |id={{proQuest|169950437}}}} The office stories are served by 97 elevator cabs; due to the presence of the double-deck elevators, these occupy 83 shafts. As designed, one bank of single-deck elevators connected the lobby to the lowest 28 stories. Banks of double-deck elevators traveled to "sky lobbies" at the 33rd/34th and 66th/67th floors, where passengers could transfer to local elevators. The 34th through 103rd stories were served by local elevators that operated from the sky lobbies. Two elevators also ran directly from the lobby to the Skydeck on the 103rd floor.{{Cite news |last=Nagelberg |first=Alvin |date=April 11, 1971 |title=Glass Elevators Give Hotel Lift |pages=49 |work=Chicago Tribune |url=https://www.newspapers.com/clip/109146093/glass-elevators-give-hotel-liftalvin/ |access-date=September 7, 2022}} {{As of|2018}}, the elevators carried 5.8 million passengers per year.

Six of the elevators are used for freight. One of the freight elevators served all stories, traveling to a height of {{convert|1440|ft}}. During a fire or another emergency, this elevator would be reserved for the Chicago Fire Department. Other elevators would be controlled from the 33rd floor. During a fire, elevators would be dispatched to the affected floors to assist with evacuation.

The building also had 16 escalators, including a set of double-height escalators that traveled from the main lobby to the lower mezzanine. Another set of escalators connects the 33rd and 34th stories.

File:Base of the Willis Tower (2021).jpg

When the building was completed, the main entrance was on Wacker Drive to the west. There was a plaza on the south side of the building, sloping upward toward Franklin Street to the east. The Franklin Street side of the building was {{Convert|6|ft}} lower than the Wacker Drive entrance, so the entrances on Franklin Street were actually below the plaza, leading to the building's lower mezzanine. Below ground level are three basement levels with a total area of {{convert|400000|ft2}}. The basements included a 1,200-seat cafeteria, commercial space, service areas, and a loading dock for 17 trucks. The basement also contained a 150-spot parking garage.

{{As of|2022}}, the building's base covers {{convert|463000|ft2}} and contains two lobbies for tenants. The building's tenants primarily enter from Wacker Drive and Franklin Street. Shoppers, restaurant patrons, and visitors to the Skydeck observation deck use the southern entrance on Jackson Boulevard. The Wacker Drive lobby contains In the Heart of this Infinite Particle of Galactic Dust, a 2019 artwork by Jacob Hashimoto. It consists of over 7,000 rice-paper and resin disks that are hung from the ceiling.{{cite web |last=Koziarz |first=Jay |date=July 16, 2019 |title=Cloud-like sculpture of 7,000 hanging disks floats above Willis Tower lobby |url=https://chicago.curbed.com/2019/7/16/20696661/willis-tower-renovation-art-jacob-hashimoto |access-date=September 7, 2022 |website=Curbed Chicago}} To honor Khan's contributions to skyscraper engineering design, the Structural Engineers Association of Illinois also commissioned a sculpture of him for the lobby of the Willis Tower.{{cite web |title=Fazlur Khan Sculpture |url=https://www.seaoi.org/history-past-presidents-khan-sculpture |access-date=February 25, 2014 |publisher=SEAOI}}

The commercial complex at the building's lowest stories is known as the Catalog, a reference to Sears' mail-order catalogs.{{cite web |last=Selvam |first=Ashok |date=October 16, 2019 |title=Inside Willis Tower's $500 Million Renovation, Which Includes New Restaurants and a Food Hall |url=https://chicago.eater.com/2019/10/16/20914831/willis-tower-new-restaurants-food-walkthrough-catalog-eq-office-urbanspace-photos-images-food-hall |access-date=September 7, 2022 |website=Eater Chicago}} The six-story complex includes numerous restaurants. It extends into three of the building's basement levels, as well as the three-story annex to the south and west of the tower. The roof of the annex includes a curved skylight with 240 glass panes, and the northern section of the annex's roof is supported by black columns that resemble those in the original tower. The Catalog also contains decorative details, such as handrails and staircase landings, which are inspired by elements of Chicago's "built environment".{{cite web |last=Koziarz |first=Jay |date=October 15, 2019 |title=Checking in on Willis Tower's new retail and dining complex |url=https://chicago.curbed.com/2019/10/15/20914151/willis-tower-renovation-construction-retail-food-hall-catalog |access-date=September 7, 2022 |website=Curbed Chicago}} The third story of the Catalog contains a 30,000-square-foot coworking space operated by Convene.

File:Willis tower skyboxes (1).jpg

File:Willis Tower glass box.jpg

The Willis Tower observation deck, called the Skydeck, opened on June 22, 1974. Located on the 103rd floor, {{convert|1353|ft|m|1}} above ground level, it is the highest observation deck in the United States{{cite web | title=One World Trade Center in New York to surpass Willis Tower in Chicago as tallest building in US | website=ABC7 New York | date=November 12, 2013 | url=https://abc7ny.com/archive/9322666/ | access-date=November 20, 2023}} and one of Chicago's most famous tourist attractions.{{cite web |last1=Rackl |first1=Lori |title=Chicago spot makes TripAdvisor's list of world's top tourist attractions in 2019 |url=https://www.chicagotribune.com/travel/ct-trav-most-popular-tourist-attractions-tripadvisor-1216-20191216-c5cjsjufrfdhriwzdvty2cfcge-story.html |publisher=Chicago Tribune |access-date=October 12, 2021 |date=December 15, 2019}} Tourists can experience how the building sways in wind and see far over the plains of Illinois and across Lake Michigan to Indiana, Michigan, and Wisconsin in clear conditions. Elevators reach the top in about 60 seconds, allowing occupants to feel the change in pressure as they ascend. Some 1.7 million tourists visit annually {{as of|2018|lc=y}}.{{cite web | last=Lewis | first=Sophie | title=Protective layer of Willis Tower's SkyDeck cracks under visitors' feet | website=CBS News | date=June 12, 2019 | url=https://www.cbsnews.com/news/willis-towers-skydeck-chicago-cracks-protective-layer-under-visitors-feet-2019-06-12/ | access-date=November 20, 2023}}{{cite web | last=Ori | first=Ryan | title=Willis Tower owner seeks thousands of new visitors per day, as $500 million expansion takes shape | website=Chicago Tribune | date=September 13, 2018 | url=https://www.chicagotribune.com/columns/ryan-ori/ct-biz-willis-tower-expansion-ryan-ori-20180907-story.html | access-date=November 20, 2023}} There is also an event venue on the 99th floor.{{cite web | title=Chicago Event Venues | website=Skydeck Chicago | date=April 25, 2023 | url=https://theskydeck.com/private-events/ | access-date=November 20, 2023}}

In January 2009, a major renovation of the Skydeck began, including the installation of retractable glass balconies which extend approximately {{convert|4|ft|m}} from the facade of the 103rd floor, overlooking South Wacker Drive. The all-glass boxes, informally dubbed "The Ledge", allow visitors to see the street below. The boxes, which can accommodate {{convert|5|ST|MT|abbr=off}}, opened to the public on July 2, 2009.[https://www.usatoday.com/travel/destinations/2009-07-01-sears-tower-glass-balconies_N.htm "Sears Tower unveils 103rd floor glass balconies"], USA Today, July 1, 2009{{cite web|url=http://www.som.com/content.cfm/sears_tower_observation_deck|title=The Ledge at Skydeck Chicago|access-date=May 15, 2011|archive-url=https://web.archive.org/web/20110608034757/http://www.som.com/content.cfm/sears_tower_observation_deck|archive-date=June 8, 2011|url-status=dead}} SOM.com Project Page On May 29, 2014, the laminated glass flooring of one of the boxes cracked while visitors were inside, but there were no injuries.{{cite web|author=BJ Lutz |url=http://www.nbcchicago.com/news/local/chicago-willis-tower-sky-deck-ledge-crack-261079001.html |title=Coating on Willis Tower Skydeck's Ledge Cracks Under Tourists |publisher=Nbcchicago.com |date=May 30, 2014 |access-date=August 26, 2014}} The flooring of the same box cracked again on June 12, 2019.{{cite web|author=Sophie Lewis |url=https://www.cbsnews.com/news/willis-towers-skydeck-chicago-cracks-protective-layer-under-visitors-feet-2019-06-12/ |title=Protective layer of Willis Tower's SkyDeck cracks under visitors' feet |publisher=cbsnews |date=June 12, 2019|access-date=June 12, 2019}} In May 2022 a fifth glass ledge opened on the west facade overlooking South Wacker Drive.

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{{Wide image|WillisTowerPanorama01.jpg|2300px|Panorama of Chicago skyline as seen from Willis Tower Skydeck||center|}}

File:Dubai-CN-Sears-towers.svg, Dubai; CN Tower, Toronto; Willis Tower, Chicago|alt=]]

When completed, the Sears Tower was the world's tallest building but not the world's tallest structure. Toronto's CN Tower was about {{convert|350|ft|m|1}} taller,{{cite news |last=Metz |first=Tim |date=March 4, 1974 |title=Where's the Highest Structure in World? Well, It's Not Chicago: New Toronto Tower May Kill Birds and Induce Vertigo, But Some Think It's Great |page=1 |work=The Wall Street Journal |issn=0099-9660 |id={{ProQuest|133852336}}}} although the Council on Tall Buildings and Urban Habitat (CTBUH) does not consider the CN Tower to be a building, since it does not have floors from the ground up.{{cite web |url=http://www.ctbuh.org/Resources/TallestDatabase/tabid/123/Default.aspx |title=CTBUH Tall Building Database |access-date=April 10, 2008 |publisher=Council on Tall Buildings and Urban Habitat |archive-url=https://web.archive.org/web/20081025030731/http://www.ctbuh.org/Resources/TallestDatabase/tabid/123/Default.aspx |archive-date=October 25, 2008 |url-status=dead }} The Willis Tower remains the third tallest building in the Americas and in the Western Hemisphere (after One World Trade Center and Central Park Tower in New York City). With a pinnacle height of {{convert|1729|ft|m|1}}, it is the third-tallest freestanding structure in the Americas. It is the 16th-tallest freestanding structure in the world by pinnacle height.

When the Petronas Twin Towers in Kuala Lumpur, Malaysia, was completed in 1998, it claimed to be the tallest building in the world, measuring {{convert|1482.6|ft|m|1}} tall including decorative spires. Chicagoans objected to this claim on the basis that the Sears Tower's top floor was higher than that of either of the Petronas Towers.{{harvnb|Kamin|2001|p=109|ps=.}} In the ensuing controversy, four categories of "tallest building" were created. Of these, Petronas was the tallest in the category of height to the top of architectural elements, meaning spires but not antennas.{{note label|talleststatus}}{{cite web |title=Height: The History of Measuring Tall Buildings |url=http://ctbuh.org/AboutCTBUH/History/MeasuringTall/tabid/1320/language/en-US/Default.aspx |url-status=dead |archive-url=https://web.archive.org/web/20120410072709/http://www.ctbuh.org/AboutCTBUH/History/MeasuringTall/tabid/1320/language/en-US/Default.aspx |archive-date=April 10, 2012 |access-date=May 1, 2012 |work=Council on Tall Buildings and Urban Habitat}} Taipei 101 in Taiwan claimed the record in three of the four categories in 2004, surpassing the Petronas Twin Towers in spire height and the Sears Tower in roof height and highest occupied floor. People suggested that Sears add cosmetics atop its tower to surpass Taipei 101, but this did not materialize.{{Cite web|url=http://www.cwoptimists.org/gghids/willis-tower-foundation.html|title = Willis tower foundation}}https://www.mountrainierpark.com/taipei-101-vs-sears-tower/{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }} With this, you would actually be looking down to Taipei 101's top floor. On August 12, 2007, the Burj Khalifa in Dubai was reported by its developers to have surpassed the tower in all height categories.{{cite web |url=http://www.visitdubai.info/news/burjdubai.htm |title=Burj Khalifa surpasses the height of Sears Tower in Chicago |publisher=Visitdubai.info |date=December 9, 2007 |access-date=October 31, 2011 |archive-url=https://web.archive.org/web/20090321204348/http://www.visitdubai.info/news/burjdubai.htm |archive-date=March 21, 2009 |url-status=dead }} Upon completion, One World Trade Center in New York City surpassed the Willis Tower through its structural and pinnacle heights, but not by roof, observation deck elevation, or highest occupied floor.{{cite web|title=Freedom Tower ("World Trade Center 1")|url=http://www.nyc-tower.com/stats/|publisher=NYC Tower|access-date=November 30, 2008|archive-url=https://web.archive.org/web/20081221032032/http://www.nyc-tower.com/stats/|archive-date=December 21, 2008|url-status=dead}}

Until 2000, the tower did not hold the record for being the tallest building by pinnacle height. From 1969 to 1978, this record was held by John Hancock Center, whose antenna reached a height of {{convert|1500|ft|m|1}}, {{convert|49|ft|m|1}} taller than the Sears Tower's original height. One World Trade Center became taller by pinnacle height with the addition of a 359-foot (109.4-meter) antenna, bringing its total height to {{convert|1728|ft|m|1}}. In 1982, two antennas were installed which brought its total height to {{convert|1707|ft|m|1}}, making it taller than the John Hancock Center but not One World Trade Center. However, the extension of the tower's western antenna in June 2000 to {{convert|1729|ft|m|1}} allowed it to just barely claim the title of tallest building by pinnacle height.

The lowest level of the Willis Tower is {{Convert|43|ft|m}} below the elevation of Franklin Street.{{Cite web |title=Willis Tower Fun Facts {{!}} Fun Facts for Children |url=https://theskydeck.com/for-kids/fun-facts/ |access-date=November 8, 2020 |website=Skydeck Chicago |language=en-US}}

File:View down from the Sears-Willis Tower Skydeck.jpg

On May 25, 1981, Dan Goodwin, wearing a homemade Spider-Man suit while using suction cups, camming devices, and sky hooks, and despite several attempts by the Chicago Fire Department to stop him, made the first successful outside ascent of the tower. Goodwin was arrested at the top after the seven-hour climb and was later charged with trespassing. Goodwin stated that the reason he made the climb was to call attention to shortcomings in high-rise rescue and firefighting techniques. After a lengthy interrogation by Chicago's District Attorney and Fire Commissioner, Goodwin was officially released from jail.{{cite web |url=http://www.justonebadcentury.com/chicago_cubs_history_47.asp |title=Chicago Cubs History and News – Welcome to Just One Bad Century |publisher=Justonebadcentury.com |access-date=October 31, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120320062017/http://www.justonebadcentury.com/chicago_cubs_history_47.asp |archive-date=March 20, 2012 }}{{cite news|url=https://query.nytimes.com/gst/fullpage.html?res=9B03E2DD1538F935A15756C0A967948260 |title=Sears Tower in Chicago Is Scaled by Stunt Man |newspaper=New York Times |date=May 26, 1981 |access-date=October 31, 2011}}

In August 1999, French urban climber Alain "Spiderman" Robert, using only his bare hands and bare feet, scaled the building's exterior glass and steel wall all the way to the top. A thick fog settled in near the end of his climb, making the last 20 stories of the building's glass and steel exterior slippery.{{cite news|url=http://www.cnn.com/US/9908/20/tower.climber/ |title='Spiderman' scales Sears Tower in Chicago – August 20, 1999 |publisher=CNN |access-date=September 14, 2009}}

Annually, since 2009, the Willis Tower has hosted SkyRise Chicago, the world's tallest indoor stair climb, as a charity event benefiting Shirley Ryan AbilityLab, where participants can (legally) climb the Willis Tower's 103-story staircase.{{cite web |last1=Pathieu |first1=Diane |title=Hundreds of stair climbers reach new heights for annual SkyRise Chicago at Willis Tower |url=https://abc7chicago.com/society/hundreds-of-stair-climbers-race-up-willis-tower-for-annual-skyrise-chicago/5668302/ |website=ABC 7 Chicago |date=November 4, 2019 |access-date=May 10, 2020}}

File:Willis Tower.jpg

Sears sold the tower in 1994 and vacated it by 1995, but retained naming rights through 2003. The new owners were rebuffed in renaming deals with CDW Corp in 2005 and the U.S. Olympic Committee in 2008. British insurance broker Willis Group Holdings leased more than {{convert|140000|sqft|m2}} of space on three floors in 2009. A Willis spokesman said the naming rights were obtained as part of the negotiations at no cost to Willis{{cite news|url=http://www.chicagotribune.com/business/chi-talk-willis-towerjul16,0,4222230.story|date=July 16, 2009|title=Sears Tower Now Willis|work=Chicago Tribune|access-date=July 16, 2009|archive-url=https://archive.today/20120703141848/http://articles.chicagotribune.com/2009-07-16/news/0907160161_1_sears-tower-hush-changed|archive-date=July 3, 2012|url-status=dead}} and the building was renamed the Willis Tower on July 16, 2009.{{cite news|url=http://www.chicagotribune.com/business/chi-talk-willis-towerjul16,0,4222230.story|title=Sears Tower name change: Building today officially becomes Willis Tower|first=Mary Ellen|last=Podmolik|date=July 16, 2009|work=Chicago Tribune|access-date=July 16, 2009|archive-url=https://archive.today/20120703141848/http://articles.chicagotribune.com/2009-07-16/news/0907160161_1_sears-tower-hush-changed|archive-date=July 3, 2012|url-status=dead}}

The naming rights are valid for 15 years, so it is possible that the building's name could change again as soon as 2024.{{cite news|url=http://www.chicagotribune.com/business/chi-talk-willis-towerjul16,0,4222230.story|title=Burns on Business, Willis Wants to be Part of Chicago by Way of Jersey|first=Greg|last=Burns|date=July 16, 2009|work=Chicago Tribune|access-date=July 16, 2009|archive-url=https://archive.today/20120703141848/http://articles.chicagotribune.com/2009-07-16/news/0907160161_1_sears-tower-hush-changed|archive-date=July 3, 2012|url-status=dead}} The Chicago Tribune joked that the building's new name reminded them of the oft-repeated "What you talkin' 'bout, Willis?" catchphrase from the American television sitcom Diff'rent Strokes and considered the name-change ill-advised in "a city with a deep appreciation of tradition and a healthy ego, where some Chicagoans still mourn the switch from Marshall Field's to Macy's".{{cite journal |last1= Podmolik|first1= Mary Ellen|year= 2009 |title= Sears Tower name change has few Chicago fans – Willis Tower may have trouble winning over public|journal=Chicago Tribune|issue= March 13, 2009|url= http://www.chicagotribune.com/business/chi-fri-willis-tower-0313-mar13,0,1361480.story}} This feeling was confirmed in a July 16, 2009, CNN article in which some Chicago-area residents expressed reluctance to accept the Willis Tower name,{{cite news|url=http://www.cnn.com/2009/US/07/16/sears.tower.renamed/index.html|title=Sears Tower Now Named Willis Tower|date=July 16, 2009|publisher=CNN|access-date=July 17, 2009}} and in an article that appeared in the October 2010 issue of Chicago magazine that ranked the building among Chicago's 40 most important, the author pointedly refused to acknowledge the name change and referred to the building as the "Sears Tower".{{cite journal|last1= Johnson|first1= Geoffrey|year= 2010|title= Top 40 Buildings in Chicago|journal= Chicago|issue= October 2010|url= http://www.chicagomag.com/Chicago-Magazine/October-2010/Top-40-Buildings-in-Chicago/index.php?cparticle=4&siarticle=3|access-date= October 12, 2010|archive-date= December 24, 2018|archive-url= https://web.archive.org/web/20181224074342/https://www.chicagomag.com/Chicago-Magazine/October-2010/Top-40-Buildings-in-Chicago/index.php?cparticle=4&siarticle=3|url-status= dead}} Time magazine called the name change one of the top 10 worst corporate name changes and pointed to negative press coverage by local news outlets and online petitions from angry residents.{{cite magazine| url=http://www.time.com/time/specials/packages/article/0,28804,1914815_1914808_1914812,00.html| archive-url=https://web.archive.org/web/20100222031252/http://www.time.com/time/specials/packages/article/0,28804,1914815_1914808_1914812,00.html| url-status=dead| archive-date=February 22, 2010| title=Top 10 Worst Corporate Name Changes: It's the Sears Tower|last=Suddath| first=Claire| magazine=TIME| date=February 8, 2010|access-date=February 8, 2010}} The naming rights issue continued into 2013, when Eric Zorn noted in the Chicago Tribune that "We're stubborn about such things. This month marked four years since the former Sears Tower was re-christened Willis Tower, and the new name has yet to stick."{{cite journal|last1= Zorn|first1= Eric|year= 2013|title= Change of Subject – "Thillens Stadium" is no more|journal=Chicago Tribune|issue= June 24, 2013|url= http://www.chicagotribune.com/news/local/ct-oped-0623-zorn-20130623,0,7213374.column|access-date= June 23, 2013|archive-url= https://web.archive.org/web/20130622095657/http://www.chicagotribune.com/news/local/ct-oped-0623-zorn-20130623,0,7213374.column|archive-date= June 22, 2013|url-status=dead}}

File:Antenna of Willis Tower, Chicago, IL.jpg

Many broadcast station transmitters are located at the top of the Willis Tower. Each list is ranked by height from the top down. Stations at the same height on the same mast indicate the use of a diplexer into the same shared antenna. Due to its extreme height, FM stations (all class B) are very limited in power output.

NOAA Weather Radio station KWO39 transmits off the tower at 162.550 MHz. Programmed by the National Weather Service Weather Forecast Office in Chicago, it is equipped with Specific Area Message Encoding (SAME), which sets off a siren on specially programmed weather radios to alert of an impending hazard.

The building has appeared in numerous films and television shows set in Chicago such as Ferris Bueller's Day Off, where Ferris and company visit the observation deck.{{cite web |url=http://www.movie-locations.com/movies/f/ferris.html |title=Filming Locations for Ferris Bueller's Day Off |publisher=Movie-locations.com |access-date=September 14, 2009 |archive-url=https://web.archive.org/web/20090430072431/http://www.movie-locations.com/movies/f/ferris.html |archive-date=April 30, 2009 |url-status=dead }} Late Night with Conan O'Brien introduced a character called The Sears Tower Dressed In Sears Clothing when the show visited Chicago in 2006.{{cite web|url=http://www.nbc5.com/video/9204958/index.html |title=The Sears Tower Dressed In Sears Clothing |publisher=Nbc5.com |access-date=October 31, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20080302213015/http://www.nbc5.com/video/9204958/index.html |archive-date=March 2, 2008 }} The building is also featured in History Channel's Life After People, in which it and other human-made landmarks suffer from neglect without humans around, collapsing two hundred years after people are gone.{{cite web|author=Keith Darcé |url=http://www.signonsandiego.com/uniontrib/20070131/news_1n31ads.html |title=Madison Avenue turns to Main Street|work=The San Diego Union-Tribune |date=January 31, 2007 |access-date=September 14, 2009}}

In the 2008 film The Dark Knight, it is part of Gotham City.{{Cite web |date=October 17, 2013 |title=The Dark Knight helped spawn a filmmaking boom in Chicago |url=https://www.avclub.com/the-dark-knight-helped-spawn-a-filmmaking-boom-in-chica-1798163383 |access-date=September 3, 2022 |website=The A.V. Club |language=en-us}} In the 2011 film Transformers: Dark of the Moon, it is featured in a number of scenes.{{Cite web |title='Transformers' jumpers up in birdland |url=https://www.chicagotribune.com/entertainment/ct-xpm-2011-06-29-ct-ent-0630-transformers-jumpers-20110629-story.html |access-date=September 3, 2022 |website=Chicago Tribune|date=June 29, 2011 }} In the 2013 film Man of Steel, the tower is the location of the offices of the Daily Planet.{{cite web|url=http://www.chicagobusiness.com/article/20110907/NEWS07/110909951/willis-tower-cbot-building-star-in-superman-filming|title=Willis Tower, CBOT Building star in Superman filming|access-date=July 26, 2013|date=September 7, 2011|publisher=ChicagoBusiness|author=Merrion, Paul}}

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{{Portal|Chicago|Illinois|Architecture}}

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• Architecture of Chicago
• List of buildings with 100 floors or more
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{{Reflist|30em}}

• {{cite book |last=Kamin |first=Blair |url=https://books.google.com/books?id=7CQLnNUkMk4C |title=Why Architecture Matters: Lessons from Chicago |publisher=University of Chicago Press |year=2001 |isbn=978-0-226-42322-7}}
• {{cite book |last1=Pridmore |first1=Jay |url=https://books.google.com/books?id=-dZQDwAAQBAJ |title=Chicago Architecture and Design |last2=Larson |first2=George A. |publisher=ABRAMS |year=2018 |isbn=978-1-68335-421-5|edition=3rd }}

{{Commons category|Willis Tower}}

• {{Official website|http://www.willistower.com/}} Willis Tower office-space leasing website
• [http://www.theskydeck.com/ Willis Tower Skydeck website]
• [https://web.archive.org/web/20191223043034/http://www.skyscrapercenter.com/building/willis-tower/169 Willis Tower] on CTBUH Skyscraper Center
• {{Cite web |url=https://www.emporis.com/buildings/117064 |archive-url=https://web.archive.org/web/20150923101516/https://www.emporis.com/buildings/117064 |url-status=usurped |archive-date=September 23, 2015 |title=Willis Tower |work=Emporis}}
• {{Structurae|id=20000065|title=Willis Tower}}

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