What is the United States?

Last reviewed: October 31, 2026

The United States of America (USA) is a federal republic in North America made up of 50 states, a federal district (Washington, D.C.) and five inhabited territories. With about 342 million people, it is the third most populous country in the world. Each state has its own constitution, legislature and supreme court, and all of them answer to a federal Constitution. That structure is the first key to understanding American politics, law and daily life.

The USA in key facts

USA, US, America: what is the difference?

"USA," "US" and "the United States" all mean the same country. Americans usually say "the U.S." or "America," and "American" is the normal word for a citizen. Elsewhere in the Americas that use can seem presumptuous, since "America" also names two continents. The country is therefore not a continent: it occupies a large part of North America, between Canada and Mexico, with Alaska to the northwest and Hawai'i in the Pacific.

How the country was formed

Thirteen British colonies on the Atlantic coast declared independence in 1776 and won it in 1783. Over the next century the country expanded to the Pacific by purchase, war and treaty, at the expense of Native nations and Mexico. New territories became states one by one. Our summary of US history gives the full timeline. That origin matters: the states came first and created the federal government, and they have defended their powers ever since.

A federation, not a unitary country

From a European vantage point, it is tempting to imagine the U.S. as a France or a U.K., with a single national government making the laws and running schools, hospitals and police. That model does not apply. Power is split across three levels:

• The federal government in Washington, D.C., handling defense, foreign policy, currency, interstate commerce, immigration and large social programs such as Social Security and Medicare.
• The 50 state governments, in charge of most of daily life: education, most criminal and civil law, roads, licensing, labor rules and family law.
• Tens of thousands of local governments (counties, municipalities, school districts, special-purpose districts) that carry out much of the day-to-day work.

Whenever you read about an American rule, the right reflex is to ask: "is this federal, state or local?" The answer changes which authority is in charge and which courts apply.

The 50 states: small republics

An American state is not a "region" in the European sense. It has its own institutions, modeled on the federal ones but autonomous:

• A state constitution, often longer and more detailed than the federal one.
• A governor elected by popular vote.
• A legislature, almost always with two chambers; Nebraska, with one, is the exception.
• A court system, with a highest court that has the final word on state law.
• Its own flag, symbols and, often, a strong sense of identity.

The states have very different histories. Some began as colonies older than the country itself (Virginia, Massachusetts), others joined in the 19th century (Texas, California), and the last two, Alaska and Hawai'i, became states only in 1959. The country's geography is just as varied; see our guide to the regions of the United States.

Why state laws vary so much

• Income tax: nine states do not tax wages (Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, Wyoming), while California's top rate is above 13%. Washington has adopted a 9.9% tax on income over $1 million, due to start in 2028 and under challenge.
• Firearms: depending on the state, buying a handgun may require a permit and a waiting period, or little beyond the federal background check at a licensed dealer.
• Cannabis: a majority of states allow it in some form, yet recreational cannabis remains illegal under federal law. In 2026 federal authorities moved certain state-licensed medical products to a less restrictive category, and a broader change is still under review.
• Marriage, divorce, custody, inheritance: these are state-law topics, with real differences between, say, Louisiana (whose civil law reflects its French and Spanish past) and the rest of the country.
• Driving: each state issues its own driver's license, sets speed limits and writes its own road rules.

Bottom line: phrases like "U.S. law on X" are often misleading; the right question is which jurisdiction applies. More in states vs federal government.

The Constitution as common ground

The U.S. Constitution, written in 1787, ratified in 1788 and in effect from 1789, sets the ground rules. Short by modern standards, it:

• Defines the powers of the federal government and separates them among the executive (President), legislative (Congress: Senate and House) and judicial (Supreme Court) branches.
• Leaves to the states, or the people, the powers it does not delegate to the federal government (Tenth Amendment).
• Lists fundamental rights through the Bill of Rights, the first ten amendments, ratified in 1791: freedom of speech, religion and the press, the right to bear arms, due process.
• Is hard to amend: normally a two-thirds vote of both chambers of Congress, then ratification by three-quarters of the states. That is why only 27 amendments have been added in over two centuries.

The Constitution outranks federal statutes, and valid federal law outranks state law. When a state law clashes with the Constitution, federal courts, and ultimately the Supreme Court, can strike it down.

D.C. and the territories

• Washington, D.C. is the federal district where national institutions are based. Its residents vote for President (D.C. has three electoral votes) but have only a non-voting delegate in the House and no senators.
• The five inhabited territories are Puerto Rico, Guam, the U.S. Virgin Islands, the Northern Mariana Islands and American Samoa. Residents are U.S. citizens, except in American Samoa, where people born there are U.S. nationals. Territory residents do not vote in the general presidential election.

Who lives there

The United States is a country of immigration: roughly one resident in seven was born abroad, and about one in five identifies as Hispanic or Latino. Native peoples, the descendants of enslaved Africans, and people with origins in Europe, Latin America and Asia make up a society far less uniform than its image abroad. To go further, read about American values and common misconceptions.

Related articles:

• How the U.S. government works
• States vs federal government
• USA vs Europe
• US history