Alcatraz Island 1906 San Francisco earthquake, civilian prisoners were transferred to Alcatraz for safe confinement. On March 21, 1907, Alcatraz was officially designated as the Western U.S. Military Prison, later Pacific Branch, U.S. Disciplinary Barracks, 1915. In 1909 construction began on the huge concrete main cell block, designed by Major Reuben Turner, which remains the island's dominant feature. It was completed in 1912. To accommodate the new cell block, the Citadel, a three-story barracks, was demolished down to the first floor, which was actually below ground level. The building had been constructed in an excavated pit (creating a dry "moat") to enhance
Alcatraz Federal Penitentiary as it was conjectured that they drowned in the bay and their bodies swept out into the sea due to the turbulent bay currents. The most violent escape attempt occurred on May 2–4, 1946, when a failed attempt by six prisoners led to the Battle of Alcatraz, also known as the "Alcatraz Blastout". It was carried out by six prisoners; Bernard Coy, Joseph Cretzer, Sam Shockley, Clarence Carnes, Marvin Hubbard and Miran Thompson. They daringly took control of the cell house by overpowering correctional officers, and were able to enter the weapons room, where they then demanded keys to the