The U.S. military used this end of Santa Rosa Island for over 100 years. Fort Pickens, the first of four forts built to protect Pensacola Bay, had an unusual history because Union forces still held the fort during the Civil War in the 1860s even though Florida was a Confederate state. As artillery technology changed, the U.S. Army later made major changes to Fort Pickens and built reinforced concrete batteries on the island starting in 1894. Between 1900 and 1910, wooden buildings were constructed to support the Coast Artillery Corps in its coastal defense role. One building, new in a photograph taken around 1900, served at different times as a guardhouse with quarters for three sergeants, a mess and kitchen, and finally as an administration building for the 13th Coast Artillery in 1945. Sibley tents lined the railroad track just west of Fort Pickens.