Oahu,Hawaii, the state's most populous island and the third largest island in the Hawaiian group. Oahu is nicknamed the Gathering Place and is often referred to as the Main Island. It lies in the North Pacific Ocean between the islands of Kauai and Molokai, about 2,400 miles (3,860 km) southwest of San Francisco, California. The area is 593 square miles (1,536 km2).
Oahu is of volcanic origin and consists mainly of a broad interior valley situated between the Waianae and Koolau ranges—two parallel mountain ranges trending southeast-northwest. The Waianae Range is the higher of the two, reaching a maximum elevation of 4,025 feet (1,227 m) at Kaala peak.
Volcanic cones made of solidified ash occur on the island. Most famous is Diamond Head, in Honolulu. Oahu also has scenic waterfalls, coastal cliffs, sandy beaches, and offshore coral reefs. Temperatures average between about 70° and 80° F. (21° and 27° C.) during all months of the year.
The tourist industry is a major economic activity on Oahu. It centers mainly in Honolulu, Hawaii's capital and largest city. Military installations also contribute heavily to the island's economy. Most of the bases are in the Pearl Harbor area, just west of Honolulu. The growing and processing of pineapples and sugarcane are important in the valley. Some light manufacturing is done in Honolulu.