Alcatraz Islan, sometimes informally referred to as simply Alcatraz or by its pop-culture name, The Rock, is a small island located in the middle of San Francisco Bay in California, United States. It served as a lighthouse, then a military fortification, then a military prison followed by a federal prison until 1963. It became a national recreation area in 1972 and received landmarking designations in 1976 and 1986.