Washington, D.C.

Washington, D.C. is the capital city of the United States. The population of the city is 591,833 and metro population is about 5.3 million. The city is not in a state but in a small district called "the District of Columbia". Washington is the only city in the District of Columbia. This is the smallest, but most densely populated United States division, fitting about 600 thousand people into an area less than 100 miles.