The United States of America is a federal republic consisting of 50 states, a federal district (where the nation's seat of government–Washington, D.C.–is located), five major territories, and various possessions. The 48 contiguous states and Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is in the northwestern part of North America (also bordering Canada) and the state of Hawaii is an archipelago in the mid-Pacific. The territories are scattered about the Pacific Ocean and the Caribbean Sea.

A state of the United States of America is one of the 50 constituent political entities that shares its sovereignty with the United States federal government. Due to the shared sovereignty between each state and the federal government, Americans are citizens of both the federal republic and of the state in which they reside. 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 sharing custody). States range in population from just under 600,000 (Wyoming) to over 38 million (California). Four—Kentucky, Massachusetts, Pennsylvania, and Virginia—use the term commonwealth rather than state in their full official names.