Guam is an island in the North Pacific Ocean. It is the largest and most populous of the Mariana Islands. Guam is 9,300 km (5,800 miles) west of San Francisco and 2,600 km (1,600 miles) east of Manila. Guam's official languages are English and Chamorro. It is an unincorporated territory of the United States. U.S. national defense spending is the main driver of Guam's economy, followed by tourism and other services.