Alcatraz Citadel, also known as Fort Alcatraz, was the original military defense and prison on Alcatraz Island, off the coast of San Francisco, California, USA. The citadel was built in 1859 as a U.S. Army military defense, and began function as a war camp in 1861 and long-term military prison in 1868. During the American Civil War, the citadel and its batteries provided an important line of defense. The island continued to develop in the 1870s and 1880s, and in 1893, the first hospital on Alcatraz opened. A new upper prison was built in 1904, but after the citadel ceased function as a military defense in 1907 and the original citadel collapsed the following year, a $250,000 concrete military prison was erected between 1910 and 1912. In 1933-4, this was modernized and became the Alcatraz F