Windley Key Fossil Reef Geological State Park is a Florida State Park

Florida State Parks

The Florida State Parks encompass the majority of the lands that fall under the authority of the Florida Department of Environmental Protection. There are 160 such entities, including nature reserves, recreation areas, and historic sites, which can be found in every corner of the state...

 located at mile marker 85.5 near Islamorada. It was a former quarry

Quarry

A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...

 used by Henry Flagler in the early 1900s to help his building of the Overseas Railroad

Overseas Railroad

The Overseas Railroad was an extension of the Florida East Coast Railway to Key West, a city of almost 30,000 inhabitants located 128 miles beyond the end of the Florida peninsula...

. Following the railroad's completion, it was a source for decorative stone pieces called Keystone

Keystone (limestone)

Keystone refers to a type of limestone, or coral rag, quarried in the Florida Keys, in particular from Windley Key fossil quarry, which is now a State Park of Florida...

. Now on display are exposed sections of fossilized coral, as well as some of the original quarry machinery. The Hurricane Monument

Labor Day Hurricane of 1935

The 1935 Labor Day Hurricane was the strongest tropical cyclone of the 1935 Atlantic hurricane season, and one of the most intense hurricanes to make landfall in the United States in recorded history...

 at Mile Marker 82 in Islamorada is constructed of keystone

Keystone (limestone)

Keystone refers to a type of limestone, or coral rag, quarried in the Florida Keys, in particular from Windley Key fossil quarry, which is now a State Park of Florida...

from the quarry.