Definition of a "Buoy" - "an anchored FLOAT serving as a navigational mark, to indicate reefs or other hazards or for mooring". The southernmost buoy's claim to fame is being one of the most photographed and visited attractions in the United States. The buoy is an impressive 12' tall, 7' wide and made out of approximately 4 tons of solid concrete!
The current marker actually didn't exist until 1983 when it was commissioned and installed by the City of Key West and painted by local artist Danny Acosta.