randomWalks

The original boundaries of the Capital City encompassed a ten-mile square, or an area of 100 square miles, in a diamond shape with north, east, south and west corners as indicated in the diagram. Four boundary stones were placed to mark these four corners of the diamond. Smaller stones were added at one mile intervals between the four corners for a total of 40 stones. ...

Born in 1731, Benjamin Banneker, was the free, self-taught mathematician and astronomer known as the "first black man of science" and part of Andrew Ellicott's survey team that laid out the boundary of the District of Columbia, at the direction of George Washington. Banneker fixed the position of the first boundary stone by lying on his back to find the exact starting point for the survey of the District, and plotting six stars as they crossed his spot at a particular time of night. This first cornerstone was set on April 15, 1791, and marked the south corner stone of the District of Columbia. From that location, the surveyors advanced northwest into Virginia and then crossed the Potomac into Maryland.

Origins of Arlington (with map!)

In a retrocession in 1847, the Federal government returned Virginia's portion. This former piece of the District of Columbia today forms the County of Arlington and a section of the City of Alexandria, Virginia. ... Many of those old stones remain in place, including some marking the pre-1847 boundary.

Washington, DC Boundary Stones (with photos)

I've only seen the southern and northern stones, but now I want to visit them all or watch a documentary about them.