Pearl Harbor is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. Much of the harbor and surrounding lands is a United States Navy deep-water naval base. It is also the headquarters of the United States Pacific Fleet. The U.S. government first obtained exclusive use of the inlet and the right to maintain a repair and coaling station for ships here in 1887. The attack on Pearl Harbor by the Empire of Japan on December 7, 1941 was the immediate cause of the United States' entry into World War II.HistoryPearl Harbor was originally an extensive shallow embayment called Wai Momi (meaning, “Waters of Pearl”) or Puuloa (meaning, “long hill”) by the Hawaiians. Puuloa was regarded as the home of the shark goddess, Kaahupahau, and her brother (or son), Kahiuka, in Hawaiian legends. According to tradition, Keaunui, the head of the powerful Ewa chiefs, is credited with cutting a navigable channel near the present Puuloa saltworks, by which he made the estuary, known as "Pearl River," accessible to navigation. Making due allowance for legendary amplification, the estuary already had an outlet for its waters where the present gap is; but Keaunui is typically given the credit for widening and deepening it.