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 Prisons. The purpose of this transfer was to punish those involved in the rampant crime which prevailed in the country in the 1920s and 1930s. The United States Disciplinary Barracks on Alcatraz was acquired by the United States Department of Justice on October 12, 1933, and the island became a Federal Bureau of Prisons federal prison in August 1934. The $260,000 conversion to the federal prison took place from January 1934. George Hess of the United States Public Health Service was appointed the chief medical officer of the prison and Edward W. Twitchell became a consultant in psychiatry for Alcatraz