Northern Mariana Islands in the context of "Contiguous United States"

Territories of the United States are subnational geographical and political areas governed as administrative divisions and dependent territories under the sovereignty of the United States. Despite all being subject to the constitutional and territorial jurisdiction of the U.S. federal government, territories differ from states and Indian reservations in that they are not inherently sovereign. While states have dual sovereignty and Native American tribes have tribal sovereignty in relation to the federal government, the self-governing powers of territories ultimately derive from the U.S. Congress, as per the Territorial Clause in Article IV of the U.S. Constitution. Territories are classified as "organized" or "unorganized" depending on whether they operate under an organic act, and "incorporated" or "unincorporated" depending on whether the U.S. Constitution applies fully or partially to them. As areas belonging to, but not integral parts of, the U.S., territories are their own distinct nations centered around a collective identity based on their land, history, ethnicity, culture, and language.

All territories of the U.S. are insular areas. The U.S. has sovereignty over three archipelagos or islands in the Caribbean Sea and eleven in the Pacific Ocean. Five territories (American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands) are permanently inhabited, unincorporated territories; the other nine are small islands, atolls, and reefs with no native (or permanent) population. Of the 14, only one is classified as an incorporated territory (Palmyra Atoll). Two additional territories (Bajo Nuevo Bank and Serranilla Bank) are claimed by the U.S. but administered by Colombia. Historically, territories were created to administer newly acquired land, and most eventually attained statehood. The most recent territory to become a U.S. state was Hawaii on August 21, 1959.

Commonwealth is a term used by two unincorporated territories of the United States in their full official names. These are the Northern Mariana Islands, whose full name is Commonwealth of the Northern Mariana Islands, and Puerto Rico, which is named Commonwealth of Puerto Rico in English and Estado Libre Asociado de Puerto Rico in Spanish, translating to "Free Associated State of Puerto Rico." The term was also used by the Philippines during most of its period under U.S. sovereignty, when it was officially called the Commonwealth of the Philippines.

The definition of commonwealth according to 2013 United States Department of State policy, as codified in the department's Foreign Affairs Manual, reads: "The term 'Commonwealth' does not describe or provide for any specific political status or relationship. It has, for example, been applied to both states and territories. When used in connection with areas under U.S. sovereignty that are not states, the term broadly describes an area that is self-governing under a constitution of its adoption and whose right of self-government will not be unilaterally withdrawn by the U.S. Congress."

The Treaty of Peace between the United States of America and the Kingdom of Spain, commonly known as the Treaty of Paris of 1898, was signed by Spain and the United States on December 10, 1898, and marked the official end of the Spanish–American War. Under it, Spain relinquished all claim of sovereignty over the West Indies archipelagos and islands of Cuba and Puerto Rico in the Caribbean, the Western Pacific island of Guam in the Marianas archipelago in Micronesia, and the Western Pacific archipelago of the Philippines in Southeast Asia to the United States. The cession of the Philippines involved a compensation of $20 million from the United States to Spain.

The treaty was preceded by the Spanish-American War armistice, a preliminary peace agreement signed on August 12, 1898 in Washington, DC. The armistice formally stopped the active hostilities between Spain and the United States, requiring Spain to cede Cuba, Puerto Rico, and Guam to the United States, and to agree to the American occupation of Manila in the Philippines. The treaty came into effect on April 11, 1899, when the documents of ratification were exchanged. It was the first treaty negotiated between the two governments since the 1819 Adams–Onís Treaty.

An open border is a border that enables free movement of people and often of goods between jurisdictions with no restrictions on movement and is lacking a border control. A border may be an open border due to intentional legislation allowing free movement of people across the border (de jure), or a border may be an open border due to a lack of legal controls, a lack of adequate enforcement or adequate supervision of the border (de facto). An example of the former is the Schengen Agreement between most members of the European Economic Area (EFTA and the EU). An example of the latter has been the border between Bangladesh and India, which is becoming controlled. The term "open borders" applies only to the flow of people, not the flow of goods and services, and only to borders between political jurisdictions, not to mere boundaries of privately owned property.

Open borders are the norm for borders between subdivisions within the boundaries of sovereign states, though some countries do maintain internal border controls (for example between the People's Republic of China mainland and the special administrative regions of Hong Kong and Macau, between the United States and the unincorporated territories of Guam, the Northern Mariana Islands and American Samoa, and the Minor Outlying Islands, or between North Korea's provinces and cities). Open borders are also usual between member states of federations, though (very rarely) movement between member states may be controlled in exceptional circumstances. Federations, confederations and similar multi-national unions typically maintain external border controls through a collective border control system, though they sometimes have open borders with other non-member states through special international agreements – such as between Schengen Agreement countries as mentioned above.

The United States of America was formed after thirteen British colonies in North America declared independence from the British Empire on July 4, 1776. In the Lee Resolution, passed by the Second Continental Congress two days prior, the colonies resolved that they were free and independent states. The union was formalized in the Articles of Confederation, which came into force on March 1, 1781, after being ratified by all 13 states. Their independence was recognized by Great Britain in the Treaty of Paris of 1783, which concluded the American Revolutionary War. This effectively doubled the size of the colonies, now able to stretch west past the Proclamation Line to the Mississippi River. This land was organized into territories and then states, though there remained some conflict with the sea-to-sea grants claimed by some of the original colonies. In time, these grants were ceded to the federal government.

The first great expansion of the country came with the Louisiana Purchase of 1803, which doubled the country's territory, although the southeastern border with Spanish Florida was the subject of much dispute until it and Spanish claims to the Oregon Country were ceded to the US in 1821. The Oregon Country gave the United States access to the Pacific Ocean, though it was shared for a time with the United Kingdom. The annexation of the Republic of Texas in 1845 led directly to the Mexican–American War, after which the victorious United States obtained the northern half of Mexico's territory, including what was quickly made the state of California.

The Mariana Islands (/ˌmæriˈɑːnə/ MARR-ee-AH-nə; Chamorro: Manislan Mariånas), also simply the Marianas, are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the north-western Pacific Ocean, between the 12th and 21st parallels north and along the 145th meridian east. They lie south-southeast of Japan, west-southwest of Hawaii, north of New Guinea, and east of the Philippines, demarcating the Philippine Sea's eastern limit. They are found in the northern part of the western Oceanic sub-region of Micronesia, and are politically divided into two jurisdictions of the United States: the Commonwealth of the Northern Mariana Islands and, at the southern end of the chain, the territory of Guam. The islands were named after the influential Spanish queen Mariana of Austria following their colonization in the 17th century.

The indigenous inhabitants are the Chamorro people. Archaeologists in 2013 reported findings which indicated that the people who first settled the Marianas arrived there after making what may have been at the time the longest uninterrupted ocean voyage in human history. They further reported findings which suggested that Tinian is likely to have been the first island in Oceania to have been settled by humans.

The states and territories included in the United States Census Bureau's statistics for the United States population, ethnicity, and most other categories include the 50 states and Washington, D.C. Separate statistics are maintained for the five permanently inhabited territories of the United States: Puerto Rico, Guam, the U.S. Virgin Islands, American Samoa, and the Northern Mariana Islands.

As of April 1, 2020, the date of the 2020 United States census, the nine most populous U.S. states contain slightly more than half of the total population. The 25 least populous states contain less than one-sixth of the total population. California, the most populous state, contains more people than the 21 least populous states combined, and Wyoming, the least populous state, has a population less than any of the 31 most populous U.S. cities.