The Mason Dixon Line was marked every mile by 500 lb. limestone markers, shipped from England. The Maryland side inscribed with the letter M, the Delaware and Pennsylvania sides with the letter P.
Every 5 miles Crown Stones were placed, with the coats of arms of the Penn and Calvert families on the north and south sides respectively. Elk Township Pennsylvania’s southern border with Maryland is marked with 7 stones, including the first 5 mile Crown Stone along the westward line.
Mason and Dixon’s survey of the line between MD, VA, and PA begun in April 1765 ended October 1767, 31 miles short of the southwest corner of PA due to hostile natives at the Great Catawba Warpath. The line was later completed in 1784 by Rittenhouse and Ellicott.