Transpeninsular Line

In 1751, a line was surveyed straight across the Delmarva Peninsula beginning at what at least some early Swedish settlers called Cape Hinlopen, which was later to become the southern boundary of Delaware.

If the actual Cape Henlopen near Lewes had been used as the start of the line, Delaware would be about one thousand square miles smaller, losing over a third of its current area.

In 1751 a line was surveyed from the Court-designated point on the Atlantic coast (Penn's Cape Henlopen) to the Chesapeake Bay, and in turn was used by Charles Mason and Jeremiah Dixon (of Mason–Dixon line fame) in 1763 when they were engaged to survey the north-south border between Maryland and the three southern counties of Pennsylvania, which became Delaware 13 years later).

A Transpeninsular Line marker can be found near the Fenwick Island Lighthouse, at the northern boundary of Ocean City, Maryland, located on 146th Street.

The midpoint Transpeninsular Line marker can be found on the north side of Route 54 about halfway between Delmar and Mardela Springs, Maryland.