What is the United States?

Last reviewed: April 25, 2026

The United States of America is a federal republic made up of 50 states, a federal district (Washington D.C.), and several inhabited territories. Each state runs its own Constitution, parliament, and supreme court; all of them recognize a federal Constitution that serves as a shared arbiter. Understanding that structure is the first key to navigating American politics, law, and administration.

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-scale social programs.
The 50 state governments, in charge of most of daily life: education, healthcare, civil and criminal justice, transportation, housing, local taxes, labor law, family law.
Thousands of local governments — counties, municipalities, school districts, special-purpose districts — that carry out a great deal of the day-to-day execution.

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

The 50 states: small republics

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

A state Constitution, often longer and more detailed than the federal one.
A governor elected by direct popular vote.
A legislature, almost always bicameral (state Senate + state House), with one exception: Nebraska, which is unicameral.
A court system, including a state Supreme Court that has the final word on state law.
Its own flag, symbols, sometimes an official language, and a strong sense of regional identity.

The 50 states have very different histories. Some predate the United States itself (Virginia, Massachusetts), others joined in the 19th century (Texas, California), and the last two — Alaska and Hawai'i — only became states in 1959. That historical diversity helps explain ongoing differences in law, political culture, and identity.

Why state laws vary so much

A few concrete examples:

Income tax: several states levy no state income tax at all (Texas, Florida, Nevada, Tennessee, Washington, Alaska, South Dakota, Wyoming, New Hampshire). Others, such as California, charge top marginal rates close to 13%.
Firearms: depending on the state, buying a handgun may require a permit, a waiting period, and a background check, or essentially none of those beyond minimal federal requirements.
Cannabis: still illegal at the federal level, but a majority of states now allow it in some form (medical, recreational, or both). The same product can be a regulated retail item under state law and a federal offense at the same time.
Marriage, divorce, child custody, inheritance: these are state-law topics, with real differences between, say, Louisiana (still partly Napoleonic) and the rest of the country.
Driving and roads: each state issues its own driver's license, sets its own speed limits, and writes its own road rules.

Bottom line: phrases like "U.S. law on X" are almost always wrong; the right question is which jurisdiction applies.

The Constitution as common ground

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

Defines the powers of the federal government and separates them across the executive (President), the legislative (Congress = Senate + House), and the judicial (Supreme Court) branches.
Reserves to the states everything it does not explicitly grant to the federal government (the Tenth Amendment).
Lists fundamental rights through the Bill of Rights — the first ten amendments, ratified in 1791 — including freedom of speech, religion, the press, the right to bear arms, and due process.
Is hard to amend: a two-thirds vote 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; federal statutes, within their proper domain, outrank state statutes. When a state law clashes with the Constitution, federal courts — ultimately the Supreme Court — can strike it down.

Political geography: 50 states + D.C. + territories

Beyond the 50 states sit:

Washington D.C., the federal district where national institutions are based. Its residents vote in presidential elections but only have symbolic representation in Congress.
Five inhabited territories with varying degrees of self-government: Puerto Rico, Guam, the U.S. Virgin Islands, the Northern Mariana Islands, and American Samoa. Their residents are U.S. citizens (with the partial exception of American Samoans) but do not vote for President.

Key takeaways

The United States is a federation of 50 states, not a unitary country.
Most everyday rules come from the state — sometimes from the city or county.
The federal government is powerful but has a defined, limited list of competences.
The 1787 Constitution is the glue, with rare and durable amendments.
To understand any American topic, always check which level of government is in charge.

Going further: