Washington D. C., officially the District of Columbia, is the capital of the United States of America.
The entity is a federal district that does not belong to any of the fifty states which comprise the nation; it reports directly to the Federal Government of the United States.
It is located on the banks of the Potomac River and is surrounded by the states of Virginia to the west and Maryland to the north, east, and south.
The District of Columbia has a population of 646,449 inhabitants (in 2013), according to estimates by the US Census Bureau.
The metropolitan area of Washington D.C. is the eighth largest in the United States, with more than five million residents, and the metropolitan area it forms with Baltimore has a population exceeding eight million.