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 Island self-determination, in part as a result of the publicity and awareness created by the occupation. The occupation ended on June 11, 1971. The entire Alcatraz Island was listed on the National Register of Historic Places in 1976, and was further declared a National Historic Landmark in 1986. In 1993, the National Park Service published a plan entitled "Alcatraz Development Concept and Environmental Assessment." This plan, approved in 1980, doubled the amount of Alcatraz accessible to the public to enable visitors to enjoy its scenery and bird, marine, and animal life. Today, American Indigenous groups, such as the International Indian Treaty