A U.S. state is a constituent
political entity of the
United States of America. There are currently 50 states, which are bound together in a
union with each other. Each state holds
governmental jurisdiction over a defined geographic territory, and shares its
sovereignty with the
United States federal government. Due to the shared sovereignty between each state and the federal government,
citizens of both the
federal republic and of the state in which they
 State citizenship and residency are flexible, and no government approval is required to
move between states, except for persons covered by certain types of court orders (e.g.,
paroled convicts and children of divorced spouses who are
States range in population from just under 600,000 (Wyoming) to over 39 million (California), and in area from 1,214 square miles (3,140 km2) (Rhode Island) to 663,268 square miles (1,717,860 km2) (Alaska). Four states use the term
commonwealth rather than state in their full official names.
States are divided into
counties or county-equivalents, which may be assigned some local governmental authority but are not sovereign. County or county-equivalent structure varies widely by state.
State governments are allocated power by the people (of each respective state) through their individual
constitutions. All are grounded in
republican principles, and each provides for a government, consisting of three branches:
States possess a number of powers and rights under the
United States Constitution. States and their residents are represented in the
United States Congress, a
bicameral legislature consisting of the
Senate and the
House of Representatives. Each state is also entitled to select a number of electors (equal to the total number of representatives and senators from that state) to vote in the
Electoral College, the body that directly elects the
President of the United States. Additionally, each state has the opportunity to
constitutional amendments, and, with the consent of Congress, two or more states may enter into
interstate compacts with one another.
Historically, the tasks of local
public health, regulating intrastate commerce, and local
infrastructure have generally been considered primarily state responsibilities, although all of these now have significant federal funding and regulation as well. Over time, the 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 and the rights of individuals.
The Constitution grants to Congress the authority to
admit new states into the Union. Since the establishment of the United States in 1776, the number of states has expanded from the
original 13 to 50.
Hawaii are the most recent states admitted, both in 1959. The Constitution is silent on the question of whether states have the power to
secede (withdraw) from the Union. Shortly after the
Civil War, the
U.S. Supreme Court, in
Texas v. White, held that a state cannot unilaterally do so.