The Mason-Dixon line, also called Mason's and Dixon's line, was surveyed between 1763 and 1767 by Charles Mason and Jeremiah Dixon in the resolution of a border dispute involving Maryland, Pennsylvania, and Delaware in Colonial America. It is still a demarcation line among four U.S. states, forming part of the borders of Pennsylvania, Maryland, Delaware, and West Virginia (originally part of Virginia).

Stone #19 lies in the Horseshoe Scout Reservation near Camp Horseshoe's Archery Range.