This raised octagonal pavilion, surmounted by a two-tiered cupola and lantern, was a mobile lighthouse, originally carried on a substructure of wooden screw piles on Half Moon Reef. From 1858 until it was moved in 1943, it guided ships from the Gulf of Mexico through Pass Cavallo into Matagorda Bay. It supplemented a stationary lighthouse constructed in 1852 by the U.S. government on Matagorda Island that was replaced in 1873 by a ninety-two-foot-tall structure built entirely of cast iron. Since 1979, the Half Moon Reef Lighthouse has sat just south of the causeway over Lavaca Bay.