Windley Key Fossil Reef Geological State Park

{{Short description|State park in Florida, United States}}

{{Use mdy dates|date=August 2023}}

{{Infobox Protected area

| name = Windley Key Fossil Reef Geological State Park

| iucn_category = V

| photo = WindleyKeyFRGStatePark.jpg

| map = Florida#USA

| map_caption =

| location = Monroe County, Florida, United States

| nearest_city = Islamorada, Florida

| coordinates = {{coord|24|56|57|N|80|35|46|W|region:US-FL|display=inline, title}}

| area =

| established = 1999

| visitation_num =

| visitation_year =

| governing_body = Florida Department of Environmental Protection

}}

Windley Key Fossil Reef Geological State Park is a Florida State Park located at mile marker 85.5 on US 1 near Islamorada. It was a former quarry used by Henry Flagler in the early 1900s to help his building of the Overseas Railroad. Following the railroad's completion, it was a source of decorative stone pieces called Keystone. Now on display are exposed sections of fossilized coral and some of the original quarry machinery. The Hurricane Monument at Mile Marker 82 in Islamorada is constructed of Keystone from the quarry.