On March 21, 1963, Alcatraz Federal Penitentiary in San Francisco, California, closed its doors. The prison had been America's top security prison since 1934, where notable criminals such as Al Capone, Alvin Karpis, George Kelly Barnes (“Machine Gun Kelly), Mickey Cohn and James "Whitey” Bulger were among the inmates. The closure was due to the high cost of maintaining the prison. Only three of the 36 inmates who tried to flee before the prison was closed are still unaccounted for by the U.S.