Washington , D.C. (District of Columbia) is the capital of the United States. Washington , D.C. is officially the District of Columbia , commonly referred to as Washington 's ' The District ' . It is located on the east coast of the United States, on the banks of the Potomac River in the East Coast. The Residence Act, signed on July 16, 1890, did not include the city in any other state or territory. The capital of the United States was formed on the lands of Maryland and Virginia. Source: Wikipedia.