Washington, D.C. is the capital of the United States of America and the seat of its three branches of government, as well as the federal district of the U.S. The city has an unparalleled collection of free, public museums and many of the nation's most treasured monuments and memorials. The vistas on the National Mall between the Capitol, Washington Monument, White House, and Lincoln Memorial are famous throughout the world as icons of the world's wealthiest and most powerful nation.
That which we call a District by any other... Washington, D.C., is known to locals as simply D.C. or the District, and it is rare to hear it called anything else. Locals usually use the name Washington to refer to the national government and the political world, rather than the city itself. The full title Washington, D.C., and the official name, District of Columbia, are rarely used by non-bureaucrats unless the speaker is trying to clearly distinguish the city from Washington State.