These canals and locks are a part of the first extensive system of canal and river navigation works undertaken in the United States. The idea for the canal was proposed by George Washington, when, as an engineer, surveyor and military emissary for Virginia, he saw the need for a trade route west beyond the Allegheny Mountains. In order to do create this route, it was necessary to try to tame the Potomac River which was a wild, unruly stream which only the hardiest of rivermen ever attempted.
The stone was set by the joint U.S.-Spanish survey party on April 10, 1799. Made of sandstone, it is roughly two feet high and eight inches thick. On the north side of the stone is the inscription "U.S. Lat. 31, 1799." On the south side is "Dominio de S.M. Carlos IV, Lat. 31, 1799."