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Mason-Dixon Line Crownstone, Intersection of the Tangent Line and the Transpeninsular Line, south side of Route 291 at the Maryland-Pennsylvania-Delaware Border.
Credit: Steve Fernie, AlbinoFlea, Creative Commons
Set in 1766 by Mason and Dixon, this crownstone marks the eastern boundary of the border between Maryland and Pennsylvania. Mason and Dixon marked the boundary between Maryland and Pennsylvania by placing stones marked with a P and M for the two colonies every mile and crownstones every five miles. Each crownstone included the coats-of-arms of the Calvert and the Penn families.