Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the Residence Act approved the creation of a capital district located along the Potomac River on the country's East Coast. As permitted by the U.S. Constitution, the District is under the exclusive jurisdiction of the United States Congress and is therefore not a part of any U.S. state.
The states of Maryland and Virginia each donated land to form the federal district, which included the preexisting settlements of Georgetown and Alexandria; however, Congress returned the Virginia portion in 1846. Named in honor of George Washington, the City of Washington was founded in 1791 to serve as the new national capital. Congress created a single municipal government for the whole District of Columbia after the American Civil War.
Washington, D.C., had an estimated population of 617,996 in 2011, the 25th most populous place in the United States. Commuters from the surrounding Maryland and Virginia suburbs raise the city's population to over one million during the workweek. The Washington Metropolitan Area, of which the District is a part, has a population of nearly 5.6 million, the seventh-largest metropolitan area in the country.
The centers of all three branches of the federal government of the United States are in the District, including the Congress, President, and Supreme Court. Washington is home to many national monuments and museums, which are primarily situated on or around the National Mall. The city hosts 176 foreign embassies as well as the headquarters of many international organizations, trade unions, non-profit organizations, lobbying groups, and professional associations.