CapitalWashington, D.C.Population estimate (2015)321·77 millionInternet domain extension.usCurrencyThe unit of currency is the dollar (USD), which consists of 100 cents.TerritoryThe United States is bounded in the north by Canada, east by the North Atlantic, south by the Gulf of Mexico and Mexico, and west by the North Pacific Ocean.Source: The Statesman's Yearbook 2018. Palgrave Macmillan, London Synonyms and related words