Guam is a U.S. territory in the Pacific Ocean, located in the Mariana Islands archipelago. It is the largest and southernmost island in the chain and is the largest island in Micronesia. Guam has been an important strategic location for the United States since 1898, when it was ceded to the U.S. by Spain following the Spanish-American War. Today, Guam is an unincorporated and organized territory of the United States, with its own government and economy.