The stone monument, erected April 26, 1751, marks the eastern end of the Transpeninsular Line surveyed in 1751 by John Watson and William Parsons of Pennsylvania and John Emory and Thomas Jones of Maryland. This line established the east-west boundary between Pennsylvania’s Three Lower Counties, now Delaware, and the Colony of Maryland. It also established the middle point of the peninsula, 35 miles to the west. The stone bears the coat of arms of the Calverts on the south side and the Penns on the north. It was accepted in 1760 and finally ratified in 1769 by King George III.