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 Island August 1934. Alcatraz was designed to hold prisoners who continuously caused trouble at other federal prisons. At 9:40 am on August 11, 1934, the first batch of 137 prisoners arrived at Alcatraz, arriving by railroad from the United States Penitentiary in Leavenworth, Kansas at Santa Venetia, California, before being escorted to Alcatraz, handcuffed in high security coaches and guarded by some 60 special FBI agents, U.S. Marshals and railway security officials. Most of the prisoners were notorious bank robbers and murderers. The prison initially had a staff of 155, including the first warden James A. Johnston and associate warden J.