Americans live under two governments at once. The federal government in Washington and fifty state governments each have their own constitutions, legislatures, executives, and courts, and states in turn create counties, cities, and school districts. Deciding who does what has been a central question since 1787 and remains at the heart of debates over health care, immigration, education, and policing.
This guide sorts out the jobs that belong mainly to Washington, those that belong mainly to states and localities, the large programs they share, and how disputes between them are resolved.
Local governments, created by the states, provide many of the services people use most. School districts run public schools, which get only about a tenth of their money from Washington. City and county police and sheriffs make up most of the roughly 18,000 law enforcement agencies in the country. Localities also handle zoning, water and sewer service, trash collection, parks, and local roads, often through special districts. Home rule laws give some cities broad power to govern themselves.
Many of the biggest programs are partnerships. In Medicaid, the federal government pays at least half of costs and states run the program within federal rules. Highways are built by states largely with federal fuel tax money, and unemployment insurance, food assistance, and child welfare work similarly. Disaster response starts with states and localities, with the federal government stepping in after a major disaster declaration. Federal grants come with conditions, as when Congress tied highway money to a drinking age of 21, and federal requirements that come without money are known as unfunded mandates.
The federal government has only the powers the Constitution grants it, though the necessary and proper clause and broad readings of the commerce and spending powers have stretched those powers far beyond their original scope. The Tenth Amendment reserves all other powers to the states or the people, and states hold a general police power to protect health, safety, and welfare. Some powers, such as taxing and borrowing, are concurrent, exercised by both. Historians describe a shift from dual federalism, with separate spheres, to cooperative federalism, with shared programs.
States write most criminal and civil law, including contracts, property, family law, and traffic rules, and their courts hear the great majority of cases. They license doctors, lawyers, and drivers, run prisons, set most election rules and administer elections, manage universities, and regulate insurance and utilities. Governors command their state National Guard units when not in federal service. Each state has its own constitution, usually longer and more frequently amended than the federal one.
Only the federal government can raise armed forces, conduct foreign policy, make treaties, coin money, set tariffs, run the mail, and decide who may immigrate and become a citizen. It also runs the largest social insurance programs directly, including Social Security and Medicare, and manages monetary policy through the Federal Reserve. Federal law enforcement focuses on crimes that cross state lines or involve federal interests, such as terrorism, counterfeiting, and drug trafficking.
Under the Supremacy Clause, valid federal law preempts conflicting state law. But the Supreme Court has held that Congress cannot commandeer state officials to carry out federal programs, as in Printz v. United States in 1997, and cannot coerce states with threats to withhold existing funds, as in the 2012 Medicaid ruling. States sue Washington often, with coalitions of attorneys general challenging policies of each administration. Recent flashpoints include immigration enforcement and sanctuary policies, marijuana laws that conflict with federal law, and 2025 court fights over deploying National Guard troops to cities over governors' objections.
Go deeper with federalism explained, see how each level raises money in who taxes what: federal, state, and local taxes, or look closer to home in how state government works.