Pearl Harbor 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 attack on Pearl Harbor by the Empire of Japan on Sunday , December 7 , 1941 brought the United States into World War II . History . Pearl Harbor was originally an extensive deep embayment called " Wai Nomi " ( meaning , “ pearl water ” ) or " Puuloa " ( meaning , “ long hill ” ) by the Hawaiians . Puuloa was regarded as the neighbor of the dolphin god , Kaahupahau , and his brother ( or father ) , Kahiuka , in Hawaiian legends . According to tradition , Keaunui , the head of the powerful Ewu chiefs , is credited with cutting a navigable channel near the present Puuloa saltworks , by which he made the estuary , known as " Pearl Lake , " 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 . 19th century . During the early 19th century , Pearl Harbor was not used for large ships due to its shallow entrance . The interest of United States in the Hawaiian Islands followed its whaling and trading ships in the Pacific . As early as 1820 , an " Agent of the United States for Commerce and Seamen " was appointed to look after American business in the Port of Honolulu . These commercial ties to the American continent were accompanied by the work of the American Board of Commissioners for Foreign Missions . American missionaries and their families became an integral part of the Hawaiian political body . Throughout the 1820s and 1830s , many American warships visited Honolulu . In most cases , the commanding officers carried letters from the U . S . Government giving advice on governmental affairs and of the relations of the island nation with foreign powers . In 1841 , the newspaper " Polynesian " , printed in Honolulu , advocated that the U . S . establish a naval base in Hawaii for protection of American citizens engaged in the whaling industry . The British Hawaiian Minister of Foreign Affairs Robert Crichton Wyllie , remarked in 1840 that " . . . my opinion is that the tide of events rushes on to annexation to the United States . " With the conclusion of the Civil War , the purchase of Alaska , the increased importance of the Pacific states , the projected trade with the Orient and the desire for a duty free market for Hawaiian staples , Hawaiian trade expanded . In 1865 , the North Pacific Squadron was formed to embrace the western coast and Hawaii . in the following year was assigned to cruise among the islands , " a locality of great and increasing interest and importance . " This vessel surveyed the Northwestern Hawaiian Islands toward Japan . As a result the United States claimed Midway Island . The Secretary of the Navy was able to write in his annual report of 1868 , that in November 1867 , 42 American flags flew over whaleships and merchant vessels in Honolulu to only six of other nations . This increased activity caused the permanent assignment of at least one warship to Hawaiian waters . It also praised Midway Island as possessing a harbor surpassing Honolulu ' s . In the following year , Congress approved an appropriation of $ 50 , 000 on March 1 , 1869 , to deepen the approaches to this harbor . After 1868 , when the Commander of the Pacific Fleet visited the islands to look after American interests , naval officers played an important role in internal affairs . They served as arbitrators in business disputes , negotiators of trade agreements and defenders of law and order . Periodic voyages among the islands and to the mainland aboard U . S . warships were arranged for members of the Hawaiian royal family and important island government officials . When King Lunalilo died in 1873 , negotiations were underway for the cessation of Pearl Harbor as a port for the duty - free export of sugar to the U . S . With the election of King Kalākaua in March 1874 , riots prompted landing of sailors from USS " Tuscorora " and . The British warship , , also landed a token force . During the reign of King Kalākaua the United States was granted exclusive rights to enter Pearl Harbor and to establish " a coaling and repair station . " Although this treaty continued in force until August 1898 , the U . S . did not fortify Pearl Harbor as a naval base . The shallow entrance constituted a formidable barrier against the use of the deep protected waters of the inner harbor as it had for 60 years . The United States and the Hawaiian Kingdom signed the Reciprocity Treaty of 1875 as supplemented by Convention on December 6 , 1884 , the Reciprocity Treaty was made by James Carter and ratified it in 1887 . On January 20 , 1887 , the United States Senate allowed the Navy to exclusive right to maintain a coaling and repair station at Pearl Harbor . ( The US took possession on November 9 that year ) . The Spanish - American War of 1898 and the desire for the United States to have a permanent presence in the Pacific both contributed to the decision . Naval presence ( 1899 - Present ) . Following the overthrow of the Hawaiian Kingdom , the United States Navy established a base on the island in 1899 . In 1941 , the base was attacked by the Japanese military . Over the years , Pearl Harbor 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 .