At the eastern end of Perdido Key is an area once used by the U.S. Army to defend Pensacola Bay. A three-tiered fort with a detached water battery called Fort McRee was built there between 1834 and 1839. During the Civil War, the fort was heavily damaged in a massive artillery exchange between Confederate forces at McRee and Barrancas, and Union forces at Fort Pickens and onboard the ships Niagara and Richmond in November 1861. Coastal erosion crumbled the foundations afterward. The end of the island is still called Fort McRee, and concrete Coast Artillery batteries were built there in 1899, 1900 and 1942. Battery 233 was the last built and remains today.