TP Line Mile 10, 1751, DE-MD is a roughly dressed stone set by the colonial Transpeninsular Line (TP Line) Survey on or about April 28, 1751, to demarcate the boundary between DE and MD. The stone is located along Mason Drive on the south edge of Selbyville, DE, about 11.5 miles northwest of Ocean City, MD, about 10.5 miles northeast of Pittsville, MD, about 10 miles west of the Mile 0 Stone at the Fenwick Island Lighthouse, and on the boundary line between Sussex County, DE, and Worchester County, MD. Triangulation station disk NORMAN is mounted in a drill hole in the top of the stone. The disk is in both the National Geodetic Survey and Geocaching databases as NORMAN, PID = HU1543: (visit link
) and (visit link
The stone is about 12 inches across at the bottom, about six inches thick, and projects 19 inches. The top is rounded, and the Penn and Calvert families’ armorial crests are barely discernable on the north and south faces, respectively. The datasheet for NORMAN describes the stone as “granite” but, to my eye, it is amphibolite gneiss (a specific variation of the generic “granite”). The stone is located in the center of a eight-foot by eight-foot brick patio that is enclosed by a none-foot by nine-foot post and chain fence. It is located about 220 feet east of the centerline of US Highway 113 and about 13 feet south of the south edge of Mason Drive.
To reach from the intersection of DE State Highway 54 (Lighthouse Road) and DE State Highway 1 (Coastal Highway) about 0.2 miles northeast of the Fenwick Island Lighthouse on the DE-MD state boundary in Fenwick Island, DE, go westerly on DE State Highway 54 for about 10.1 miles to the intersection with South Main Street in Selbyville, DE. Turn right and go northwest on South Main Street for about 0.2 miles to the intersection with Church Street (DE State Highway 17). Turn left and go southwest on Church Street for about 0.8 miles to the intersection with US Highway 113 (DuPont Blvd). Turn left and go south on US Highway 113 for about 0.2 miles to the intersection with Mason Drive. Turn left and go east on Mason Drive for about 220 feet to the stone on the right.
HISTORY OF THE TRANSPENINSULAR LINE
The Transpeninsular Line (TP Line) constitutes a portion of the boundary line between Delaware and Maryland. It runs almost due west from the Atlantic Ocean at Fenwick Island across the Delmarva Peninsula. It ends at the mid-point of the peninsula, about 35 miles west of its origin. The line was marked with seven historical stones. Six of the seven survive.
In 1750, after 70 years of dispute and failed negotiations between the proprietors of Delaware and Pennsylvania (the Penn Family) and the proprietors of Maryland (the Calvert Family), the Court of Chancery ruled that the southwest corner of Delaware was to be the “Middle Point” of a line running due west from Cape Henlopen on the Atlantic coast across the Delmarva Peninsula. The “Cape Henlopen” actually identified on the charts used by the Court was located at Fenwick Island, about 24 miles south of the modern Cape Henlopen.
The Court appointed four commissioners, John Watson and William Parsons of Pennsylvania and John Emory and Thomas Jones of Maryland, to run the TP Line. Most of the actual surveying work was done by Nicholas Sculls of Pennsylvania. In 1750-1751, the commissioners ran the TP Line and marked it with five gray gneiss stones – one near the initial point and one every five miles (except for the Mile 15 point) to the 25-mile point. The surveyors did not set a stone at the Mile 15 point because the point was located in the Pocomke River. Also, they did not fix the middle point of the line because the contending parties could not agree on whether the width of the peninsula should be measured all the way to the eastern shore of the Chesapeake Bay or only to the eastern reach of the Bay’s tidal waters, about four miles east of the shoreline.
In 1760, the Court ratified a “Final Agreement” between the contending parties. That agreement specified, in part, that the Middle Point would be determined with respect to the width of the peninsula measured all the way to the eastern shore of the Chesapeake Bay. The Court also accepted the survey as run in 1750 – 1751. Upon this acceptance,
the commissioners set stones at Miles 30 and 35 (Middle Point).
With the Court of Chancery’s ratification of the TP Line in 1760, colonial surveyors John Riggs, Thomas Garrett, John Lukens and Archibald McClean ran a twelve-mile radius from the New Castle courthouse and established the “Tangent Point”, where a line run a few degrees west of north from the Middle Point would intersect the Twelve-Mile Circle boundary line. In 1761, the surveyors began to run the Tangent Line (western boundary of Delaware) but, after about two years’ work, the task proved to be beyond their technical abilities. In August, 1763, the proprietors of the two colonies engaged Charles Mason and Jeremiah Dixon to survey and mark all the boundary lines between Pennsylvania and Maryland.
In November, 1763, Mason and Dixon arrived in Philadelphia. Mason and Dixon accepted without change the determination of the Middle Point as established in 1751 and ratified in 1760. In June, 1764, Mason and Dixon started their survey of the Tangent Line northward from the Middle Point.
The stones marking Miles 0, 5, 10, 20 and 35 miles survive at or near their original locations. The stone at Mile 25 was moved to avoid road construction and now is co-located with the Mile 35 stone near the Middle Point. The Mile 30 stone disappeared in the 1970’s. Both the Mile 25 and Mile 35 stones are situated in a wrought-iron enclosure along with a double crown stone set in November, 1768. The double crown stone was set by the commissioners who oversaw Mason and Dixon’s 1763 – 1767 surveys of the remaining boundary lines between Maryland and the Penn Family’s two colonies.
The TP Line stones are dark gray gneiss (specifically, perhaps, a type known as “amphibolite gneiss”). They are about 12 inches across at the bottom, about six inches thick, and the tops are rounded. The stones originally bore the armorial crests of the Penn and Calvert families on their north and south faces, respectively. The crests on the stone at Miles 0 and 5 are still readily discernable, but all the remaining stones have weathered to the point that the crests are not recognizable.
The stone at Mile 0 was originally set 2,224 feet (139 perches) west of the shoreline at the Atlantic Ocean. The nominal distances for the stones at Miles 5 through 35 originate at the shoreline (and not the initial stone). The stone at Mile 35 (as originally measured) was a few hundred feet less than 35 miles from the shoreline (because the peninsula was originally measured as 69.93 miles wide). Using the National Geodetic Survey’s INVERSE calculator, the distance between the stone at Mile 0 and the stone at Mile 35 is 34.6474 miles. Adding 2,224 feet to that measure places the Middle Point 35.0686 miles from the Atlantic shoreline today.
The agreements between the Penn and Calvert families, as well as the Court of Chancery’s rulings, specified that the TP Line was to run due west. However, the line bends a bit to the north, and the Middle Point is about 3,215 feet (0.609 miles) north of a parallel of latitude originating at Mile 0.
According to the 1994 boundary agreement between Delaware and Maryland, the surviving 1751 stones that have not been moved from their original positions continue to mark this portion of the two states’ common boundary line.
Mason, Charles and Jeremiah Dixon, “The Journal of Charles Mason and Jeremiah Dixon”, transcribed by A. Hughlett Mason (American Philosophical Society, 1969)
Bayliff, William H., The Maryland-Pennsylvania and Maryland-Delaware Boundaries, (Maryland Board of Natural Resources, Bulletin 4 Second Edition, 1959)
Bedini, Silvio A., “The Scull Dynasty of Pennsylvania Surveyors”, Professional Surveyor Magazine, May, 2001, Volume 21 Number 5.
Cummings, Hubertis M., “The Mason and Dixon Line, Story for a Bicentenary, 1763-1963”, (Commonwealth of Pennsylvania, Department of Internal Affairs, 1962)
Danson, Edwin “Drawing the Line: How Mason and Dixon Surveyed the Most Famous Border in America” (John Wiley & Sons, 2001)
Mackenzie, John “A brief history of the Mason-Dixon survey line” (University of Delaware, 2002 (?)) at (visit link
Meade, Buford K., Report on Surveys of Delaware – Maryland Boundaries, (U.S. Department of Commerce, National Oceanic and Atmospheric Administration, 1982)
Nathan, Roger E., East of the Mason-Dixon Line, (Delaware Heritage Press, 2000)
Robinson, Morgan, “Evolution of the Mason-Dixon Line” (The Journal of American History, 1909) at (visit link
Schenck, William S., “Delaware’s State Boundaries” (Delaware Geological Survey, undated) at (visit link
Wikipedia article: “Transpeninsular Line” at (visit link
Miscellaneous National Geodetic Survey datasheets and state historical signs
Also, the “State Boundaries” section of the Delaware Geological Survey (DGS) website at (visit link
) has several valuable references: Schenck, William S., “Delaware’s State Boundaries” (undated); copies of the current state boundary agreements with Maryland, Pennsylvania and New Jersey; and a database of the state’s boundary markers accessible through a “clickable” map of the state. The database comprises an inventory of all the Delaware boundary markers (modern and historic), and includes Roger Nathan’s field observations from his 1982 – 1985 inventory of the markers.