Alcatraz Citadel Alcatraz Citadel Alcatraz Citadel, also known as Fort Alcatraz, was the original military defense and prison on Alcatraz Island, off the coast of San Francisco, California, United States. 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
Alcatraz Citadel compensation for his initiative in purchasing and securing Alcatraz Island for the U.S. government, but the U.S. government later invalidated the sale and paid Fremont nothing. Fremont and his heirs sued for compensation during protracted but unsuccessful legal battles that extended into the 1890s. Following the acquisition of California by the United States as a result of the Treaty of Guadalupe Hidalgo which ended the Mexican–American War (1848), and the onset of the California Gold Rush the following year, the U.S. Army began studying the suitability of Alcatraz Island for the positioning of coastal batteries to protect the approaches to