Washington, D.C., in full District of Columbia, city and capital of the United States of America. It is coextensive with the District of Columbia (the city is often referred to as simply D.C.) and is located on the northern shore of the Potomac River at the river’s navigation head—that is, the transshipment point between waterway and land transport. The state of Maryland borders the District of Columbia to the north, east, and west, and the state of Virginia borders the District on the southern shore of the Potomac River.

Washington is an extraordinary city, one with multiple personalities: a working federal city, an international metropolis, a picturesque tourist destination, an unmatched treasury of the country’s history and artifacts, and a cosmopolitan centre that retains a neighbourly small-town ambience. The role Washington plays as the capital of the United States often overshadows its lively local history and its complex political, economic, and social issues. About half the land in Washington is owned by the U.S. government, which pays no taxes on it. Several hundred thousand people in the D.C. metropolitan area work for the federal government.

The city of Washington was built on a gently undulating, low, wide peninsula of land bounded by the Potomac River and its tributary, the Anacostia, in the belief that the location would develop into an important commercial port. (Potomac is an Algonquian word meaning “trading place,” and Anacostia is derived from the name of a local people, the Nacostines, who traded on that river.) Encircling the city are a series of terraces that in certain areas rise to about 400 feet (120 metres) above sea level, where Washington’s neighbourhoods were gradually built. Part of a shallow, long ravine—what is now Rock Creek Park—separated Washington from the old port city of Georgetown; development to the north and west of this ravine was slow until the end of the 19th century, when the ravine was bridged and public transportation was made available.

Washington has a temperate climate with high humidity levels. Precipitation throughout the year is evenly distributed, averaging between 3 and 4 inches (75 and 100 mm) per month. Winters are damp, and extremes in temperature and heavy snowfalls are not typical. The infrequent wet, light snow often melts quickly, as average winter daytime temperatures are in the mid-30s F (about 2 °C); however, freezing temperatures at night can quickly change the melted snow to ice. In the summer brief periods of high temperatures are common, often accompanied by dense humidity. The average summer daytime temperatures are in the mid-70s F (about 24 °C), but highs above 100 °F (about 39 °C) can occur. Spring and autumn are pleasantly mild and tend to be longer than summer and winter