Pearl Harbor is a U.S. Navy base on the Hawaiian island of Oahu and the headquarters of the U.S. Pacific Fleet. Adjacent to the harbour is Hickam Air Force Base, and the two installations were merged in 2010 to become Joint Base Pearl Harbor–Hickam. The USS Arizona remains where it sank on December 7, 1941, and it is preserved as a national cemetery. The USS Arizona Memorial is one of the most visited tourist attractions in Hawaii.