Due to its isolation from the outside by the cold, strong, hazardous currents of the waters of San Francisco Bay, Alcatraz was used to house Civil War prisoners as early as 1861. Following the war in 1866 the army determined that the fortifications and guns were being rapidly rendered obsolete by advances in military technology. Modernization efforts were undertaken between 1870 and 1876 but never completed. In 1867 a brick jailhouse was built (previously inmates had been kept in the basement of the guardhouse), and in 1868 Alcatraz was officially designated a long-term detention facility for military prisoners. The Fortress was deactivated as a military prison in October 1933, and transferred to the Bureau of Prisons. During World War I the prison held conscientious objectors, 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 prison in August 1934. During the 29 years it was in use, the jail held such notable criminals as Al Capone, Robert Franklin Stroud (the Birdman of Alcatraz), George "Machine Gun" Kelly,James "Whitey" Bulger, and Alvin Karpis (who served more time at Alcatraz than any other inmate). It also provided housing for the Bureau of Prison staff and their families.