Alcatraz Federal Penitentiary Alcatraz Federal Penitentiary The Alcatraz Federal Penitentiary or United States Penitentiary, Alcatraz Island (often just referred to as Alcatraz or The Rock) was a maximum high-security federal prison on Alcatraz Island, off the coast of San Francisco, California, which operated from August 11, 1934, until March 21, 1963. The main prison building was built in 1910–1912 during its time as a United States Army military prison; Alcatraz had been the site of a citadel since the 1860s. The United States Disciplinary Barracks, Pacific Branch on Alcatraz had been acquired by the United States Department of Justice on October 12, 1933,
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