The American Shoal Light is located east of the Saddlebunch Keys, just offshore from Sugarloaf Key, close to Looe Key, FL. It was completed in 1880, and first lit on July 15, 1880. The structure was built to the same plan and dimensions as the Fowey Rocks lighthouse, completed in 1878.
American Shoal Light is cast iron, with a screw-pile foundation with a platform and a skeletal tower. The Light is 109 feet (33 m) above the water. The keeper's octagonal dwelling is on a platform 40 feet (12 m) above the water. The tower framework and dwelling are painted brown, while the enclosed circular stair to the lantern is painted white. The original lens was a first-order drum Fresnel lens, producing a flash every 5 seconds. The light was automated in 1963, and a fourth-order lens with solar-powered light was installed. The light has a nominal range of 14 miles (23 km) in the white sectors, and 10 miles (16 km) in the red sectors.
American Shoal Light was built by a Trenton, NJ, firm and took only 13 months to fabricate, ship, and erect on site. The site of the lighthouse was on the outermost reefs, and was covered with 4 feet (1 m) of water. The tower when completed cost about $94,000.