Historically, the tasks of local law enforcement, public education, public health, regulating intrastate commerce, and local transportation and 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. Alaska and 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.