Article 1, Section 8, Clause 17: District of Columbia

To exercise exclusive Legislation in all Cases whatsoever, over such District (not exceeding ten Miles square) as may, by Cession of particular States, and the Acceptance of Congress, become the Seat of the Government of the United States, and to exercise like Authority over all Places purchased by the Consent of the Legislature of the State in which the Same shall be, for the Erection of Forts, Magazines, Arsenals, dock-Yards and other needful Buildings;

The Founders saw fit to establish a seat of government that would be independent of any of the states. To this end, this clause provides for a district of limited size that would be exclusively under federal control. It was to be ceded voluntarily by one or more of the states and accepted by Congress, and would then become the seat of government.

The existing district was created by Congress in 1790, and the first session of Congress in the “City of Washington” was held in 1800. The district has a local council, but its actions are subject to being overridden by Congress. The distict is not a state nor part of any state, has no voting representatives in Congress (merely a nonvoting delegate in the House), but has three electoral votes in the College of Electors, per the 23rd Amendment.

There have been various moves to make the Disrict of Columbia a state, but all have foundered on the fact that this would almost certainly require a Constitutional amendment, and the necessary high level of support to pass such an amendment is unlikely to ever be realized so long as the voters of the District continue to be highly skewed towards one of the major parties.