Alcatraz Island Engineers began fortifying the island, work which continued until 1858, eventuating in Fortress Alcatraz. The island's first garrison at Camp Alcatraz, numbering about 200 soldiers and 11 cannons, arrived at the end of that year. When the American Civil War broke out in 1861, the island mounted 85 cannons (increased to 105 cannons by 1866) in casemates around its perimeter, though the small size of the garrison meant only a fraction of the guns could be used at one time. At this time it also served as the San Francisco Arsenal for storage of firearms to prevent them falling into
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