Tonsfeldt Round Barn

{{Use mdy dates|date=March 2025}}

{{Infobox NRHP

| name = Tonsfeldt Round Barn

| nrhp_type =

| image = LeMarsIA TonsfeldRoundBarn.jpg

| caption =

| location = Plymouth County Fairgrounds, LeMars, Iowa

| coordinates = {{coord|42|47|52|N|96|09|34|W|display=inline,title}}

| locmapin = Iowa#USA

| area = less than one acre

| built = 1918

| architect =

| architecture =

| added = November 19, 1986

| mpsub = {{NRHP url|id=64000152|title=Iowa Round Barns: The Sixty Year Experiment TR}}

| refnum = 86003194{{NRISref |refnum=86003194|2008a}}

}}

The Tonsfeldt Round Barn is a historic building located on the Plymouth County Fairgrounds in LeMars, Iowa, United States. It was built in 1918 to house H.P. Tonsfeldt's purebread Polled Hereford cattle, and prize bull, on his farm west of the city.{{cite web|url={{NRHP url|id=86003194}}|title=Tonsfeldt Round Barn|publisher=National Park Service|access-date=2017-11-24|author=}} with {{NRHP url|id=86003194|photos=y|title=photo}} The building is a true round barn that measures {{convert|82|x|68|ft}}.{{cite web|url=http://www.dalejtravis.com/rblist/rbia.htm|title=Iowa Round Barn List|publisher=Round Barns & Covered Bridges|access-date=2011-01-06|author=Dale Travis}} The barn features white horizontal siding, an aerator and a Gothic curved roof. The self-supporting Gothic-arch dome of this barn is a unique feature on Iowa's round barns. In 1981 the barn was moved from the farm to the fairgrounds in order to preserve it. It is now used for exhibit space. The barn has been listed on the National Register of Historic Places since 1986.