Located on U.S. Highway 1, at approximately mile markers 84--85.5, between Plantation Key and Upper Matecumbe Key.

DeBrahm chart (1772) shows Wright. Gerdes, in his "Reconnaissance of the Florida Reefs and all the Keys" (1849) states: "Island between Long Id. (Plantation Key) and Old Matacumbe has no name." U.S. Coast Survey "Sketch Showing the Positions of the Beacons on the Florida Reefs" (1855) shows Vermont Key. A U.S. Army report written in 1857 by Capt. Abner Doubleday uses Vermont Key. A survey map drawn by Charles Smith in 1873 shows Windley Island. A fishing guide written by William H. Gregg in 1902 has Windy Island. The Cruise of the Barbee, written in 1916 by John Kunkle Small, refers to this key as Umbrella Key, then has Windleys Island in parentheses. A map published by the F.E.C. Railway prior to 1935 shows Windley's Island.

Prior to the building of the Florida East Coast Railway, there were two separate islands here, known as the Umbrella Keys. Railway construction Involved filling between these two which then became known as Windley Key, after a settler. This is the site of several extensive quarries which for many years supplied building stone, known locally as keystone. The railway station on Windley Key was known as Quarry.