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 legendary prison" suited to the times, which resulted in the Alcatraz Island Federal Penitentiary being nicknamed "Uncle Sam's Devil's Island." Despite Alcatraz being designed to house the "worst of the worst" of criminals who caused problems at other prisons, under the guidelines and regulations set by the strict prison administrators, courts could not direct a prisoner to be directly sent to Alcatraz, however notorious they were for misbehavior and attempted escape from other prisons. Prisoners entering Alcatraz would undergo vigorous research and assessments prior to their arrival. Security in the prison was very tight, with the constant checking of bars,