Alligator Reef Light

Alligator Reef Light is located 4 nautical miles (7.4 km; 4.6 mi) east of Indian Key, near the Matecumbe Keys of Florida in the United States, north of Alligator Reef itself. The station was established in 1873. It was automated in 1963 and was last operational in July, 2014, and is being replaced by a 16' steel structure with a less powerful light located adjacent to it. The structure is an iron-pile skeleton with a platform. The light is 136 feet (41 m) above the water. It is a white octagonal pyramid skeleton framework on black pile foundation, enclosing a square dwelling and a stair-cylinder. The lantern is black. The original lens was a first order bivalve Fresnel lens. The light characteristic of the original light was: flashing white and red, every third flash red, from SW by W 1/2 W through southward to NE 1/8 E, and from NE by E 3/4 E through northward to SW 3/8 S; flashing red throughout the intervening sectors; interval between flashes 5 seconds. It has a nominal range of 14 nautical miles (26 km; 16 mi) in the white sectors and 11 nautical miles (20 km; 13 mi) in the red sectors. The new light will have a range of approximately 7 nautical miles (13 km; 8.1 mi).

• http://en.wikipedia.org/wiki/Alligator Reef Light