In the Micronesia subregion of the western Pacific Ocean, the United States has an organized, unincorporated territory called Guam Chamorro Guhan. It is the United States' westernmost point and territory (derived from its geographic center); Hagta, its capital, is further west than Melbourne, Australia, at 144°57'47"E. In Oceania, Guam is the biggest and southernmost of the Mariana Islands and the biggest island in Micronesia. Dededo is the village with the most people, and Hagta is the capital of Guam.

While Guam delegates to the United States House of Representatives do not have the right to vote on the floor, people who were born on Guam are considered citizens of the United States even though they do not have the right to vote in presidential elections while they are residing on Guam. The Chamoru, also known as the Chamorro in the past, are the indigenous Guamanians. They are related to the Austronesian peoples of Indonesia, the Philippines, Malaysia, Taiwan, Micronesia, and Polynesia, as well as Polynesia. Guam's population is 168,801 as of 2022. On the multiethnic island, the Chamoros are the largest ethnic group but a minority. The territory covers 540 km2 or 210 square miles; 130,000 acres) and a population density of 775 inhabitants per square mile (299 inhabitants per km2) The island was settled by Chamoro people approximately 3,500 years ago. On March 6, 1521, Portuguese explorer Ferdinand Magellan visited the island for the first time while serving Spain. In 1668, Spain established a colony on Guam. The Spanish Manila Galleons made Guam an important stopover between the 16th and 18th centuries. Guam was taken over by the United States on June 21, 1898, during the Spanish–American War. In accordance with the December 10, 1898 Treaty of Paris, Spain gave Guam to the United States on April 11, 1899.