Most people know that Alcatraz was once a world-famous federal penitentiary, but the Island’s history before and after the penitentiary era is less well known. For example, few realize that it was also the site of the first American lighthouse on the West Coast and that the Island served as a huge harbor defense fort during the Civil War. After the fort became obsolete, the U.S. Army turned the Island into a grim military prison. Following the closing of the penitentiary, Alcatraz became the site of an American Indian protest movement that would change modern American history.