Arcadia Publishing As one of America's most notorious prisons, Alcatraz has been a significant part of California's history for over 155 years. The small, lonely rock, known in sea charts by its Spanish name "Isla de los Alcatraces," or "Island of Pelicans," lay essentially dormant until the 1850s, when the military converted the island into a fortress to protect the booming San Francisco region. Alcatraz served as a pivotal military position until the early 20th century and in 1934 was converted into a federal penitentiary to house some of America's most incorrigible prisoners. The penitentiary closed in 1963, and Alcatraz joined the National Park Service system in 1972. Since then, it has remained a popular attraction as part of the Golden Gate National Recreation Area.