Boundary Markers of The Original District of Columbia - Geography

Geography

The District of Columbia was originally specified to be a square 100 square miles (260 km2) in area, with the axes between the corners of the square running north-south and east-west, and having its southern corner at the southern tip of Jones Point in Alexandria, Virginia, at the confluence of the Potomac River and Hunting Creek (later the site of the Jones Point Lighthouse). The sides of the square are each 10 miles (16 km) long. The specified orientation results in a diamond shape for the District's original boundaries on most maps.

The north-south axis of the District's current boundaries extends between present 17th and 18th Streets, N.W., continuing south across the National Mall to the far shore of the Potomac River; the east-west axis is between present Constitution Avenue and C Street, N.E. and N.W. Note that these axes are not the lines used to define the four geographical quadrants of the District (N.E., N.W., S.E., and S.W.), commonly appended to Washington street addresses, which are delimited generally by North Capitol Street, East Capitol Street, South Capitol Street, and the National Mall. The center of the square is west of the Ellipse and north of the Mall, within the grounds of the headquarters of the Organization of American States.

In 2011, the District of Columbia geographic information system (GIS) program completed a project to map the District’s boundary using Global Positioning System (GPS) and contemporary survey technology at an accuracy of +/- 5 centimetres (1.97 in) horizontally and +/- 9 centimetres (3.54 in) vertically. The GIS program's survey found that (listed in the order in which Andrew Ellicott's team performed the initial boundary survey):

• Along the northwest boundary, the stones are outside the existing boundary ranging from 4.43 feet (1.35 m) to 9.6 feet (2.93 m)
• Along the northeast boundary, the stones are inside the existing boundary ranging from 6.6 feet (2.01 m) to 8.4 feet (2.56 m)
• Along the southeast boundary, the stones are outside the existing boundary ranging from 12.75 feet (3.89 m) to 18.48 feet (5.63 m)

The overall accuracy of the historic survey and the survey using 2011 technology produced remarkably similar results. For example, the distance between Southeast stones numbers 6 and 7 is 5,280.824 feet (1,609.5952 m), almost exactly one mile (5,280 feet (1,609.3440 m)).