Guam was colonized in 1670.
Guam ( [ ˈɡwɑːm ] or [ ˈɡwɒm ] Chamorro : Guåhån [ ˈɡʷɑhɑn ] formally the Territory of Guam ) is an unincorporated and organized territory of the United States . Guam was colonized in 1668 with settlers , like Diego Luis de San Vitores , a Catholic missionary . Under the Treaty of Paris , Spain ceded Guam to the United States on December 10 , 1898 .