The United States is composed of 50 states, which are constituent political entities sharing sovereignty with the federal government, meaning Americans are citizens of both their state and the nation, with the freedom to move between states without government approval. Each state operates under its own constitution, grounded in republican principles, and features three separate branches of government—executive, legislative, and judicial—while being subdivided into counties for local administration. States hold significant powers, including representation in the bicameral U.S. Congress, participation in the Electoral College, the ability to ratify constitutional amendments, and the recognized "police power" to govern for the public good. Historically, states have managed local law enforcement, education, and infrastructure, but over time the federal government has grown more centralized, fueling an ongoing debate over states' rights. Starting with the 13 original colonies in 1776, the Union expanded to 50 states, while the Supreme Court's landmark ruling in Texas v. White (1869) established that states cannot unilaterally secede from the Union.