The famous Mason & Dixon Line marks the border between Pennsylvania and Maryland, and culturally, the demarcation between the northern and southern United States.  Along the Great Allegheny Passage, the landmark is celebrated with a replica of the surveyors’ 66-foot measurement chains that crosses the GAP surface, an obelisk denoting the Penn and Calvert families whose antagonistic boundary dispute precipitated Mason and Dixon’s survey work, and a striking set of engraved granite blocks perfect for a mid-day photo op.    

History of landmark

Surveyed between 1763 and 1767 by British astronomer Charles Mason and surveyor Jeremiah Dixon, the Mason & Dixon Line resolved a longstanding quarrel between the family of William Penn (founder of Pennsylvania) and the descendants of Charles Calvert (proprietor of Maryland) as to the legal boundary between the two colonies.  This work required precise, time-consuming measurements made using relatively simple tools — a zenith sector, a navigator’s quadrant, a direction transit, an astronomical clock, and 16.5-foot wooden rods, among others — on foot and by horseback in the rugged wilderness.  Mason and Dixon placed stones to mark each mile of the revised boundary, including especially-carved “crownstones” with family crests for both the Penns and Calverts every five miles.        

Visitor Information

The nearest trailheads are at Deal, Pa. to the west, and Frostburg, Md, to the east.