Is the United States an Empire?

An empire is a state that imposes durable, unequal power over territories or peoples beyond—or subordinated within—its political core. By that standard, the United States has combined continental settler empire, formal overseas colonialism and informal or neo-colonial dominance. The mix changed, but imperial power did not disappear.

Continental expansion displaced Indigenous nations through warfare, forced removal, broken treaties and settler occupation. The Louisiana Purchase doubled the claimed national domain in 1803; the United States annexed Texas in 1845; the Mexican–American War ended in 1848 with Mexico ceding roughly 529,000 square miles under the Treaty of Guadalupe Hidalgo. Indigenous sovereignty persisted despite US claims.

Overseas expansion accelerated in 1898. The United States annexed Hawaiʻi and, after defeating Spain, took Puerto Rico, Guam and the Philippines. Cuba became formally independent in 1902 but remained constrained by the Platt Amendment, imposed in 1901, which authorised US intervention and enabled the Guantánamo Bay lease.

“The policy of this country ought to be to stop expansion.” — Mark Twain, 1900, “To the Person Sitting in Darkness”

Today, Washington still possesses Puerto Rico, Guam, American Samoa, the US Virgin Islands and the Northern Mariana Islands. Their residents have unequal political rights: none elects voting members of Congress, and residents generally cannot vote for president while living in a territory. See the archive’s overview of the American empire and its account of neo-colonies.

Four bodies of evidence support the imperial classification.

1. Territorial conquest and annexation. The United States grew from 13 states in 1790 to a transcontinental state after wars, purchases, settler seizure and coerced Indigenous cessions. The Indian Removal Act of 1830 facilitated expulsions including the Cherokee Trail of Tears in 1838–1839.
2. Colonial government. Congress retains plenary authority over US territories under Article IV of the Constitution. The Supreme Court’s Insular Cases, beginning in 1901, created the doctrine that some constitutional protections did not fully apply in “unincorporated” territories—a racialised framework that remained operative in 2026.
3. Military reach. The US Department of Defense’s Base Structure Report for fiscal year 2018 listed 4,775 sites worldwide, including 514 overseas. David Vine’s 2020 research estimated approximately 800 US bases outside the 50 states, depending on whether smaller, classified and shared facilities are counted.
4. Intervention without annexation. US forces occupied Haiti from 1915 to 1934 and the Dominican Republic from 1916 to 1924. The Central Intelligence Agency helped overthrow Iran’s elected prime minister, Mohammad Mosaddegh, in 1953, and supported the operation that removed Guatemala’s elected president, Jacobo Árbenz, in 1954. The United States invaded Iraq in 2003 without annexing it.

The resulting system links military force to alliances, sanctions, aid, corporate power, unequal trade, preferred political factions and cultural influence. These mechanisms are examined under neo-colonies, while territorial rule is documented in the American empire hub.

There is no single numerical measure of empire. Scholars count different things: territorial possessions, military sites, interventions, occupations or states subjected to decisive influence.

Measure	Source and year	Estimate	What it includes
Overseas military sites	US Department of Defense, fiscal year 2018	514	Officially reported sites outside the 50 states
Overseas bases	David Vine, 2020	About 800	Publicly known large and small installations across roughly 80 countries and territories
Foreign interventions	Congressional Research Service, 2023	Hundreds since 1798	Instances of US armed forces used abroad; definitions and duration vary
Territorial jurisdictions inhabited by civilians	US government status in 2026	5 principal territories	Puerto Rico, Guam, American Samoa, US Virgin Islands and Northern Mariana Islands

The figures are not directly interchangeable. The Pentagon counts properties through administrative rules that can consolidate multiple facilities, omit some shared sites and treat territories as domestic. Vine uses a broader geopolitical definition. Either total describes a military presence unmatched in geographic distribution by any contemporary state.

The strongest evidence is cumulative: annexed territories, subordinated populations, hundreds of overseas military facilities and repeated interventions form one historical system rather than isolated exceptions.

Some diplomatic historians, officials and international-relations scholars prefer “hegemon,” “superpower” or “liberal international order.” They argue that the United States rarely annexed territory after 1945, promoted decolonisation in selected cases, built treaty alliances whose members retained sovereignty, and supplied collective goods such as maritime security. Geir Lundestad’s 1986 phrase “empire by invitation” described Western European governments requesting US protection after 1945.

The objection identifies a real distinction between formal colonies and consensual alliances, but it does not settle the wider question. Consent can coexist with hierarchy, and an invitation from an allied government says little about populations subjected to coups, occupation or sanctions. Nor does post-1945 restraint erase continuing territorial possessions or the Insular Cases.

Other critics regard “empire” as too broad if it covers both Puerto Rico and an independent NATO ally. Historians therefore distinguish formal empire, informal empire, settler colonialism and hegemony. Daniel Immerwahr’s 2019 formulation, the “Greater United States,” emphasises colonies and bases; Alfred W. McCoy’s 2017 analysis emphasises military and geopolitical dominance; William Appleman Williams’s 1959 “Open Door” thesis foregrounds overseas market access.

The most defensible answer is consequently qualified, not evasive: the United States is an empire, but its relationships vary in coercion, legal form and local agency. Calling every US alliance colonial would obscure those differences; refusing the term altogether obscures conquest and continuing colonial rule.

The classification changes what must be explained. Westward expansion becomes colonisation rather than empty-land settlement; 1898 becomes an intensification rather than the empire’s birth; and the post-1945 order appears as both alliance system and hierarchy.

It also centres political rights. In 2026, approximately 3.6 million people lived across the five principal US territories, based on recent US Census Bureau counts and estimates: Puerto Rico held roughly 3.2 million, while Guam, the US Virgin Islands, American Samoa and the Northern Mariana Islands together held roughly 400,000. Exact totals vary by census year and annual estimate. Their status raises concrete choices: statehood, independence, free association or another arrangement based on meaningful self-determination.

Recognising empire does not imply that every US foreign relationship is identical, that local governments lack agency, or that rival powers are benign. It requires tracing who makes decisions, who can refuse, who receives protection or profit, and who bears displacement, debt, sanctions, pollution or war.

For the archive, the practical consequence is to connect events often separated in national histories: Indigenous dispossession, the annexation of Hawaiʻi in 1898, the Philippine–American War of 1899–1902, Caribbean occupations, Cold War coups and contemporary base politics. That continuity is the organising argument of American empire; the indirect mechanisms are mapped through neo-colonies.

• US Department of Defense, Base Structure Report, Fiscal Year 2018
• Congressional Research Service, Instances of Use of United States Armed Forces Abroad, 1798–2023
• US Census Bureau, Island Areas
• Daniel Immerwahr, How to Hide an Empire, 2019
• David Vine, The United States of War, 2020
• Office of the Historian, Milestones: 1899–1913