Alcatraz, [Span. Álcatraces=pelicans], rocky island in San Francisco Bay, San Francisco co., W Calif., 3 mi/4.8 km NNW of downtown San Francisco and 1 mi/1.6 km N of mainland; part of city of San Francisco. First visited by the Spanish in 1769, it was named for its large pelican rookery. The Spanish fortified Alcatraz, which came under U.S. control in 1851. The isl. was used as a U.S. military prison from 1859 until 1933, when it became a Federal prison for criminals; it was closed in 1963. Nicknamed “The Rock,” it was a symbol of the impregnable fortress prison with max. security and strict discipline. The isl. became part of Golden Gate Natl. Recreation Area in 1972, which includes mainland sections on both sides of Golden Gate Channel. Golden Gate Bridge 3 mi/4.8 km to W; Angel Isl. 2 mi/3.2 km N; Treasure Isl. 2 mi/3.2 km E.
