Pearl Harbor is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It has been long visited by the Naval fleet of the United States, before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the Reciprocity Treaty of 1875. Much of the harbor and surrounding lands is now 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.
Over the years, it remained a main base for the US Pacific Fleet after World War II along with Naval Base San Diego. In 2010, the Navy and the Air Force merged their two nearby bases; Pearl Harbor joined with Hickam Air Force Base to create Joint Base Pearl Harbor-Hickam.
On February 18, 2016, a tourist helicopter fell there, injuring four people; one person was missing and is thought to be dead.
In December 2016, Japanese Prime Minister Shinzo Abe made a joint visit to Pearl Harbor with US President Barack Obama. This trip marked the 75 year anniversary of the attack, and was the first official visit by a sitting Japanese leader.
Source : wikipedia