How the US Has Grown and Shrunk Throughout History

Beyond the 50 states and Washington, D.C., the United States possesses five permanently inhabited territories and a far-flung scattering of desolate islands that mostly wildlife calls home. Although unable to elect the president or have voting representation in Congress, some 3.6 million territorial residents salute the stars and stripes, celebrate the Fourth of July and can serve in the military.

Territories have been part of America since its founding, as in the case of the Northwest Territory. The U.S. expanded further in the 19th century through diplomacy and war. Once Manifest Destiny stretched the country across the continent, offshore acquisitions in the Caribbean and Pacific began. Here’s how the United States gained possession of seven overseas territories and, in two cases, lost them.

After invading Cuba and Puerto Rico during the 1898 Spanish-American War, the United States formally took control of both Caribbean islands under the subsequent Treaty of Paris that ended Spanish colonial rule in the Americas and launched the U.S. as an imperial power. Although the U.S. withdrew from Cuba in 1902, Puerto Rico remains America’s most populous territory with an estimated 3.2 million residents. Puerto Ricans received U.S. citizenship in 1917, and a 1952 constitution made the island an autonomous commonwealth. A majority of Puerto Ricans approved a nonbinding referendum for Puerto Rican statehood in 2020, but long-standing divisions remain over whether the unincorporated territory should maintain commonwealth status or seek independence, statehood or more autonomy.

News of the Spanish-American War reached the isolated Spanish garrison on Guam so slowly that when the USS Charleston opened fire in June 1898, islanders mistook it for a ceremonial salute. Once informed a war was afoot, the Spanish governor promptly surrendered, ending two centuries of colonization. Formally ceded to America in the 1898 Treaty of Paris, the small but strategically vital island was under U.S. Navy control when Japan bombed its sparse military operations and communications facilities hours after attacking Pearl Harbor. After more than two years of Japanese occupation, the U.S. recaptured its westernmost territory on July 21, 1944. Like Puerto Ricans, Guamanians were granted U.S. citizenship in 1950.

About a week into the Spanish-American War, U.S. Commodore George Dewey’s squadron annihilated the Spanish Pacific fleet in Manila Bay, reigniting revolt against Spain’s three-century colonization of the Philippines. Despite verbal pledges to support the independence movement, the U.S. annexed the Philippines for $20 million. The rebels launched a bloody, three-year war against their new colonial foe that claimed 10 times more American troops than the war with Spain. “Once the United States took the Philippines… it became a test of U.S. prestige,” says Daniel Immerwahr, author of How to Hide an Empire: A History of the Greater United States. “It’s hard for great powers to seek to control a country, meet resistance and then immediately retreat.” America retained control until July 4, 1946, when it honored President Franklin D. Roosevelt’s 1943 pledge to grant independence after Japan’s brutal World War II occupation.

Distinct from the independent country of Samoa, this collection of seven Polynesian islands that lies closer to New Zealand than Hawaii is America’s southernmost territory. In the late 1800s, the Samoan islands served as a critical South Pacific coaling station for American commercial and navy vessels. The archipelago grew in importance after America’s acquisition of the Philippines. “Suddenly it made a lot more strategic sense for the United States to have other Pacific territories,” Immerwahr says, “so American Samoa had greater value for its place within a Pacific colonial network.” After dividing control of the Samoan Islands with Germany in 1899, the United States claimed Tutuila and its neighboring islands to the east, with Samoan chiefs formally ceding the land between 1900 and 1904. Today, its roughly 44,000 residents are U.S. nationals but not U.S. citizens.

After Colombia rejected a treaty with the U.S. to build a manmade waterway across the Panamanian isthmus, President Theodore Roosevelt recognized a Panamanian independence movement in 1903 that promptly granted America exclusive rights to build the Panama Canal. Although it didn’t own the land, the United States received for perpetuity “all the rights, power and authority” within a 10-mile-wide, 50-mile-long Panama Canal Zone. American military presence and the colonial-style administration caused friction and violent protests, including 1964 riots in which 22 Panamanian students and four U.S. soldiers died, prompting Panama to briefly cut diplomatic relations. “By the late 20th century, the cost of colonizing increasingly seems to violate professed U.S. ideals, but also it seems like the United States can get what it needs from the Panama Canal without directly controlling it,” Immerwahr says. To that end, President Jimmy Carter signed treaties that dissolved the Canal Zone in 1979 and returned full control of the waterway to Panama in 1999, though the U.S. retained the right to use military force to keep the canal open.

The acquisition of the U.S. Virgin Islands—home to some 100,000 people—was a real estate transaction 50 years in the making. In 1867, Secretary of State William Seward negotiated the purchase of the Caribbean islands then known as the Danish West Indies from Denmark, only to have the U.S. Senate reject it. The Danish parliament took its turn blocking a deal in 1902. Concerned that Germany would annex Denmark in World War I and use its Caribbean islands as a naval or submarine base, Secretary of State Robert Lansing made another unsuccessful offer then suggested the U.S. might seize the territory if rebuffed again. Denmark then agreed to a $25 million sale in 1916, with U.S. recognition of Danish authority over Greenland as part of the deal. St. Croix, St. John, St. Thomas and dozens of smaller islands officially joined the U.S. in 1917, and islanders became American citizens 10 years later.

America’s most recent territorial acquisition includes Saipan and 13 neighboring islands northeast of Guam. After seizing the Micronesian islands from Japan during World War II, the United States served as sole administrator of a strategic trust under United Nations sovereignty. Following Guam’s rejection of four separate votes for unification by residents of the Northern Mariana Islands in the 1950s and 1960s, U.S. Congress approved their establishment as an American commonwealth in 1976. With a population of some 51,000, the Northern Marianas officially became an American territory after the U.N. formally dissolved its trusteeship a decade later. Residents were granted immediate U.S. citizenship.