Alcatraz Federal Penitentiary and the island became a prison of the Federal Bureau of Prisons in August 1934 after the buildings were modernized to meet the requirements of a top-notch security prison. Given this high security and the location of Alcatraz in the cold waters and strong currents of San Francisco Bay, the prison operators believed Alcatraz to be escape-proof and America's strongest prison. Alcatraz was designed to hold prisoners who continuously caused trouble at other federal prisons. One of the world's most notorious and best known prisons over the years, Alcatraz housed some 1,576 of America's most ruthless criminals including Al Capone,
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