The Ten Mile Square

Article 1, Section 8, Clause 17 of the United States' Constitution declares that the Congress has the right:

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.

Such a District was created on 16 July 1790 when the square of ten mile sides was carved from Maryland and Virginia. The portion on the southern side of the Potomac River was returned to Virginia in 1847.

In the early 1970s, surveyors placed boundary stones at one mile intervals on the perimeter of the Ten Mile Square. Most of these can still be found today.