Washington, D.C. is the capital city of the United States of America. "D.C." is an abbreviation for the District of Columbia, the federal district coextensive with the city of Washington. The city is named after George Washington, military leader of the American Revolution and the first President of the United States. The District of Columbia and the city of Washington are coextensive and are governed by a single municipal government. For most practical purposes, they are considered to be the same entity, though this was not always the case. As late as 1871, when Georgetown ceased to be a separate city, there were multiple jurisdictions within the District. Although there is a municipal government and a mayor, Congress has the supreme authority over the city and district, which results in citizens having a different status and less representation in government than residents of the states.

Washington, D.C. is located at 38°53′42″N, 77°02′11″W (the coordinates of the Zero Milestone, on the Ellipse). According to the United States Census Bureau, the city has a total area of 68.3 square miles (177.0 km²). 61.4 square miles (159.0 km²) of it is land and 6.9 square miles (18.0 km²) of it (10.16%) is water. Washington is surrounded by the states of Maryland (on its southeast, northeast, and northwest sides) and Virginia (on its western side); it interrupts those states' common border, which is the Potomac River's southern shore both upstream and downstream from the District. The Potomac River as it passes Washington is virtually entirely within the District of Columbia border because of colonial riparian rights between Maryland and Virginia.