Washington, D.C. is the capital of the United States, a planned federal district occupying 68 square miles on the Potomac River between Maryland and Virginia. Home to the three branches of the U.S. federal government, world-class Smithsonian museums, iconic monuments, and a vibrant multicultural dining and arts scene, the city draws more than 24 million visitors annually. Most of the capital's major museums and memorials are free, making it one of the most accessible great cities on earth.