US Map, Map of US – How Many Are There

A U.S. state is a federated state of the United States of America that shares its sovereignty with the United States federal government. Since the admission of Hawaii as a state in August 1959, there have been fifty U.S. states. Because of the shared sovereignty between a U.S. state and the U.S. federal government, an American is a citizen of both the federal entity and of his or her state of domicile. State citizenship and residency are flexible and no government approval is required nor obtained to move between states, except for persons covered by certain types of court orders (e.g., paroledconvicts and children of divorced spouses who are sharing custody). States are further subdivided into counties or county-equivalents, which may or may not be assigned some individual governmental authority. Kentucky, Massachusetts, Pennsylvania, and Virginia use the official title of Commonwealthrather than State.

The United States Constitution allocates certain powers to the federal government. It also places limitations on the federal and state governments. State governments are allocated power by the people (of each respective state) through their individual constitutions. By ratifying the United States Constitution, the States transferred certain limited sovereign powers to the federal government. Under the Tenth Amendment, all powers not delegated to the federal government nor prohibited to the states are retained by the states or the people. Historically, the tasks of public safety (in the sense of controlling crime),public education, public health, transportation, and infrastructure have generally been considered primarily state responsibilities, although all of these now have significant federal funding and regulation as well (based largely upon the Commerce Clause, the Taxing and Spending Clause, and the Necessary and Proper Clause of the U.S. Constitution).

Over time, the U.S. Constitution has been amended, and the interpretation and application of its provisions have changed. The general tendency has been toward centralization and incorporation, with the federal government playing a much larger role than it once did. There is a continuing debate over states’ rights, which concerns the extent and nature of the states’ powers and sovereignty in relation to the federal government as well as the rights of individual persons. Debates over states’ rights were a contributing factor in the outbreak of the American Civil War.

The U.S. Congress may admit new states on an equal footing with existing ones; this last happened in 1959 with the admission of Alaska and Hawaii. The U.S. Constitution is silent on the question of whether states have the power to leave unilaterally, or secede from, the Union, but the U.S. Supreme Court has ruledsecession to be unconstitutional, a position driven in part by the outcome of the American Civil War.

List of U.S. states