<P> Guam (/ ˈɡwɑːm / (listen); Chamorro: Guåhån (ˈɡwɑhɑn)) is an unincorporated and organized territory of the United States in Micronesia in the western Pacific Ocean . It is the westernmost point (in terms of jurisdiction) and territory of the United States, along with the Northern Mariana Islands . The capital city of Guam is Hagåtña and the most populous city is Dededo . The inhabitants of Guam are called Guamanians, and they are American citizens by birth . Indigenous Guamanians are the Chamorros, who are related to other Austronesian natives to the west in the Philippines and Taiwan . </P> <P> In 2016, 162,742 people resided on Guam . Guam has an area of 210 square miles (540 km; 130,000 acres) and a population density of 775 per square mile (299 / km). In Oceania, it is the largest and southernmost of the Mariana Islands and the largest island in Micronesia . Among its municipalities, Mongmong - Toto - Maite has the highest population density at 3,691 per square mile (1,425 / km), whereas Inarajan and Umatac have the lowest density at 119 per square mile (46 / km). The highest point is Mount Lamlam at 1,332 feet (406 m) above sea level . Since the 1960s, the economy has been supported by two industries: tourism and the United States Armed Forces . </P> <P> The indigenous Chamorros settled the island approximately 4,000 years ago . Portuguese explorer Ferdinand Magellan, while in the service of Spain, was the first European to visit the island, on March 6, 1521 . Guam was colonized by Spain in 1668 with settlers, including Diego Luis de San Vitores, a Catholic Jesuit missionary . Between the 16th century and the 18th century, Guam was an important stopover for the Spanish Manila Galleons . During the Spanish--American War, the United States captured Guam on June 21, 1898 . Under the Treaty of Paris, Spain ceded Guam to the United States on December 10, 1898 . Guam is among the seventeen non-self - governing territories listed by the United Nations . </P> <P> Before World War II, there were five American jurisdictions in the Pacific Ocean: Guam and Wake Island in Micronesia, American Samoa and Hawaii in Polynesia, and the Philippines . </P>

Who did guam belong to before the us