In 1828, the military acquired land to construct a fort to protect Pensacola Bay and Pensacola Navy Yard. Construction on the fort began in 1829 and was completed in 1834. It is one of the largest brick forts built in the United States. Between 1890 and the 1940s, other structures, concrete gun batteries, and a rifle range were added around the island: however, as more advanced weapons were developed, especially during World War II, the Fort Pickens Military Reservation became obsolete. The War Department declared the site surplus in 1948, and they transferred the land to Escambia County. In 1971, it became part of the Gulf Islands National Seashore. This Formerly Used Defense Site comprises 1,168 acres at the west end of Santa Rosa Island in Escambia County. The former Military Reservation includes the original pentagonal brick fort as well as the outlying batteries and facilities the military constructed over the years.