From 1934-1963, Alcatraz was a high-security federal prison in San Francisco Bay. With a reputation of being escape-proof, it held notorious, high-profile prisoners, particularly those with a history of previous escape attempts.
In May 1946, after a failed escape attempt, prisoners waged a 3-day siege at Alcatraz prison. Led by a bank robber, inmates took nine guards hostage. Two guards and three prisoners were killed. Eleven guards and one uninvolved convict were also injured. Two of the surviving convicts were later executed for their roles.