The boundary between Maryland and Virginia on the mainland was simply the Potomac River, which did not need any further explanation. However, on the peninsula, the charter called for a line drawn east from Watkins point. Until the line was drawn, nobody could be sure what land belonged each province on the lower eastern shore. There were several local boundary disputes, and the problem escalated in the 1660's. Edmund Scarborough, the King's Surveyor General, led several armed excursions into Maryland claiming that the land belonged to Virginia. At this time it became imperative that a physical line finally be drawn. Phillip Calvert, Chancellor of Maryland and the Scarborough created the boundary in 1668 and reported their progress to the council of Maryland.

'... we do Conclude the same to be Watkins Point from which said Point so Called we have run an East Line agreable with the extreamest part of the Westernmost Angle of the said Watkins Point over Pocomoke River to the Land near Robert Hoistons and there have marked Certain Trees which are so Continued by an East Line Running over Swansecute Creeke into the Marsh of the Sea Side with apparent marks and Boundaries which by our mutual Agreement according to the qualifications aforesaid are to be Received as the Bounds of Virginia and Maryland on the Eastern Shore of Chesopeak Bay...' (AOM 5:43)

This line, refered to as the Calvert-Scarborough line, was supposed to be east-west, but it actually runs slightly to the northeast from Watkins point. The present-day boundary of Maryland is partially composed of this line. It can be oberved by extending the line on a map, that it does not seem to begin at Watkins Point, but rather at a site near Crisfeid, Maryland. This inaccuracy was not discovered at the time, and the line resolved the boundary disputes. Owners of land that was thought to be in Virginia, but lay on the Maryland side of the line were asssured that their patents would stay the same, but they would have to divide their taxes between both colonies

. 'It is agreed that all Persons who have Surveyed or Patented and seated Lands on the Seaboard Side in the Right of Virginia and now fallen within the divisional Line shall enjoy their said Lands they taking a Patent from the Lord Proprietary of Maryland and within seven years entring rights in the said Province and paying the half fees to the Surveyor General and full fees to the Secretary and Chancellor'(AOM 5:44)

The same applied for Maryland land found to lie in Virginia. Dispute over this boundary would rise again in the late 1800s, and result in the current boundary.