Guam (/ˈɡwɑːm/ or /ˈɡwɒm/; Chamorro: Guåhån [ˈɡʷɑhɑn]; formally the Territory of Guam) is an unincorporated and organized territory of the United States. Located in the western Pacific Ocean, Guam is one of five American territories with an established civilian government. The capital city is Hagåtña, and the most populous city is Dededo. In 2015, 161,785 people resided on Guam. Guamanians are American citizens by birth. Guam has an area of 544 km2 (210 sq mi) and a density of 297/km² (770/sq mi). 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 density at 1,425/km² (3,691/sq mi), whereas Inarajan and Umatac have the lowest density at 47/km² (119/sq mi). The highest point is Mount Lamlam at 406 meters (1,332 ft) above sea level. The Chamorros, Guam's indigenous people, settled the island approximately 4,000 years ago. Portuguese explorer Ferdinand Magellan was the first European to visit the island on March 6, 1521. Guam was colonized in 1668 with settlers, like Diego Luis de San Vitores, a Catholic missionary. Between the 1500s and the 1700s, 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 of the United Nations. Before World War II, Guam and three other territories – American Samoa, Hawaii, and the Philippines – were the only American jurisdictions in the Pacific Ocean. On December 7, 1941, hours after the attack on Pearl Harbor, Guam was captured by the Japanese, and was occupied for thirty months. During the occupation, Guamanians were subjected to culture alignment, forced labor, beheadings, rape, and torture. Guam endured hostilities when American forces recaptured the island on July 21, 1944; Liberation Day commemorates the victory. Since the 1960s, the economy is supported by two industries: tourism and the United States Armed Forces.