Alcatraz Island was originally explored as a habitat for seabirds in 1775 by Lieutenant Juan Manuel de Ayala. He named it Isla de los Alcatraces, meaning Island of the Pelicans. During the Civil War from 1861 to 1865, a prisoner of war camp was established on the island. Serving as a federal prison from 1934 to 1963, Alcatraz held some of the United States' most notorious criminals, such as Al Capone, George "Machine Gun" Kelly, and Robert Stroud, also known as the "Birdman of Alcatraz." After its closure, it became and remains a popular tourist destination.