Carysfort Reef Light is located approximately six nautical miles east of Key Largo, Florida. The lighthouse has an iron screw-pile foundation with a platform, and a skeletal, octagonal, pyramidal tower, which is painted red. The light is 100 feet (30 m) above the water. It was the oldest functioning lighthouse of its type in the United States until it was decommissioned in 2015, having been completed in 1852. Carysfort Reef is named for HMS Carysfort (1766), a 20-gun Royal Navy post ship that ran aground on the reef in 1770. The light currently installed is a xenon flashtube beacon. It was added to the National Register of Historic Places in 1984.