MASDIX Tangent Line Boundary Monument Mile 13, 1765, DE-MD, is an 11.75-inch by 12-inch Portland Stone (oolitic limestone) shaft that projects 27 inches. It was set by Charles Mason and Jeremiah Dixon at this position in 1765 to demarcate their 1764 survey of the Tangent Line. The stone is located in heavy woods about 0.54 miles southwest of Delaware State Highway 549 and 0.39 miles northeast of Maryland State Highway 577 (Reliance Road). The stone is about 5.4 miles west of Seaford, DE, 4.8 miles southeast of Federalsburg, MD, 0.95 miles north of Reliance, DE, and on the Sussex County, DE, – Caroline County, MD, boundary line. It is 13.023 miles north of the southwest corner of Delaware at BM 0 = MD-DE CORNER, PID = HU1800. The boundary stone is in both the National Geodetic Survey (NGS) and Geocaching databases as BOUNDARY MONUMENT 13 DEL MD at PID = HU2035: (
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The stone is an intermediate mile marker with a cut “M” on the west face and a cut “P” on the east face. The stone has suffered some damage, is in generally poor condition, and leans about five degrees to the southeast. The top horizontal edges are all chipped, and there is a large chip at the northeast corner of the top that runs about six inches down the northeast vertical edge of the shaft. Also, there is a two inch deep gouge about six inches about the ground on the north face, and two-inch by two-inch chip at the ground level of the southeast vertical edge. The top is roughly pyramidal. Some fluting is visible on all four faces, but none on the top. Both the cut “M” and cut “P” are in good condition. The stone is located in heavy woods, about 75 feet east of the centerline of a dim, north-south road, and 55.9 feet east of triangulation station WRIGHT (PID = HU2036) .
Mason and Dixon first surveyed this position on or about July 5, 1764, and finalized the position on or about September 27, 1764. The stone was originally set at this position on or about December 20, 1765 under their direct supervision. The US Coast and Geodetic Survey monumented it as BOUNDARY MONUMENT 13 DEL MD in 1962.
To reach from the intersection of Maryland State Highways 313, 318 and 577 on the southeast edge of Federalsburg, MD, go southeast on MD 313/577 for 1.2 miles to where MD 313 branches off to the south. Continue southeast on MD 577 for about 2.3 miles to the crossroad intersection with Oak Grove Road. Turn left and go northeast on Oak Grove Road for about one mile to the state boundary line. Continue northeast on the road for about 0.1 miles to the intersection with Delaware State Highway 549. Turn right and go southeast on DE 549 for about 0.8 miles to Longacre Lane leading southwest. Turn right and go southwest on Longacre Lane for about 0.2 miles to the gate of a restricted access biosecure poultry operation. After securing permission to continue from the operation’s manager, continue southwest between large chicken houses for about 0.25 miles to a point 50 feet southwest of the southwest end of the last chicken house on the south side of the driveway. The state boundary line crosses the driveway where a southeast-running drainage ditch meets the driveway. From this point, pack south through the woods for about 800 feet to the stone. If you pack southwesterly through the woods, you will intercept a north-south dim track road that can be followed south until you reach the stone.
HISTORY OF THE TANGENT LINE
The Tangent Line forms a portion of the boundary line between Delaware and Maryland. It runs from northward for 82 miles from the southwest corner of Delaware to a point of tangency with the Twelve-Mile Circle boundary line centered on the courthouse at New Castle, DE. During the period 1765 – 1768, the Tangent Line was marked with 83 stones. All but nine of the stones survive at or near their original surveyed positions.
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 appointed four commissioners to run the Transpeninsular Line (east-west southern boundary of Delaware) and to determine southwest corner of Delaware at the Middle Point of that line (halfway between the Atlantic Ocean and the Chesapeake Bay). In 1750-1751, the commissioners and surveyors ran and marked the Transpeninsular Line.
In 1760, the Court ratified the Transpeninsular survey and ratified a Final Agreement between the Penns and Calverts. That agreement specified, in part, that the western boundary of Delaware was to be a line (the “Tangent Line”) run northerly from the Middle Point to a point tangent (the “Tangent Point”) with the Twelve Mile Circle boundary line centered on the cupola of the courthouse at New Castle. Colonial surveyors determined the Tangent Point and attempted, unsuccessfully, to run the Tangent Line. In August, 1763, the proprietors of the two colonies engaged Charles Mason and Jeremiah Dixon to complete this line, and to survey all the boundary lines between Maryland and its neighbors to the north and east.
Mason and Dixon arrived in America in November of 1763. They started work on the Tangent Line in June, 1764, and, after running the line north and south a total of three times, completed the survey and temporary marking in November, 1764. In June, 1765, they marked the Tangent Point (the intersection of the Tangent Line and the Arc Line boundary segment) with a dark gray, gneiss stone that bore the abbreviated armorial crests of the Penns and Calverts. In December, 1765, Mason and Dixon placed the first 50 of 83 Portland Stone markers along the Tangent Line at one-mile intervals from Mile 1 through Mile 50, working from south to north. They placed 32 more stones in October – November, 1766, marking Mile 51 through 82. The stone at Mile 82 was a crown stone and it was placed a few yards south of the 1765 stone that marked the Tangent Point. In November, 1768, (about two months after Mason and Dixon departed America), the joint boundary commission set a stone at the Middle Point, the south end of the Tangent Line and the intersection with the Transpeninsular Line. The stone is a 14-inch by 14-inch Portland Stone shaft that projects about 36 inches, and is a “double crown stone” - the armorial crest of the Penn Family is cut into the north and east faces of the stone, and the crest of the Calvert Family is cut into the south and west faces. Though not set by Mason and Dixon, the Middle Point stone is generally described as a “Mason-Dixon stone”.
Mason and Dixon were assisted by three colonial surveyors: Joel Bailey, Jonathan Cope and William Darby. They also engaged the services of a small army of axmen, teamsters and other laborers.
The Tangent Line runs from the double crown stone at the Middle Point (see PID = HU1800) northward (3 degrees 36” 6’ west of north) about 82 miles to the Tangent Point. As determined by Mason and Dixon, the Tangent Point was a few yards north of Mile 82. In 1849, a survey (the “Graham Survey”) by the US Corps of Topographical Engineers (USCTE) adjusted the Tangent Point and marked it with a granite stone at PID = JU3840. Today, the original 1765 Mason-Dixon stone abuts the 1849 granite marker; the 1766 Mile 82 marker that originally stood a few yards to the south has been lost.
Along the line, the five-mile intervals are marked with stones that have the Penn and Calvert armorial crests carved on their east and west faces, respectively. The intermediate mile markers have a cut “M” on the west face and a cut “P” on the east. The stones are high-grade oolitic limestone – greater than 95 percent calcium carbonate – and were quarried near the Isle of Portland (a peninsula) on the south coast of England. The dense limestone is generically known as “Portland Stone”. The intermediate mileposts are generally 12-inches by 12-inches and about 40 inches in length, and few stones project more than 24 inches. The crown stones are about a foot longer. The vertical faces of the stones are fluted (with very shallow flutes of about 0.5 inches), with a two-inch band of horizontal fluting at the corners (with shallow flutes of about 0.4 inches). The tops originally were pyramidal and fluted. Due to weathering and damage, the tops of most stones are flat or slightly rounded. The cut letters are about five inches in height and are surrounded by an eight-inch flattened oval. Many of the stones have chiseled X’s in their tops. Most of the stones have PIDs, and about one dozen are accessible to the public. According to the Delaware Geological Survey, 76 of the original 82 (apparently not counting the Mile 82 marker near the Tangent Point) Mason-Dixon stones survive. By my count 74 of the 83 stones survive (counting the Mile 82 marker) at or near their original surveyed positions. The nine non-surviving or relocated stones are:
1. Mile 5 – missing
2. Mile 7 – missing (may be in the Naticoke River)
3. Mile 10 – moved to the Mile 79 position in 1976, moved to the Delaware Geological Survey building in 1991
4. Mile 11 – moved to a point near the Mile 42 position in 1976
5. Mile 30 – missing
6. Mile 42 – missing (may be in Mudd Mill Pond), replaced with Mile 11 stone in 1976.
7. Mile 61 – missing
8. Mile 64 – missing
9. Mile 82 – missing
I strongly suspect that the Mile 82 marker, a crown stone, now resides in the Historical Society of Delaware in Wilmington. Mason and Dixon probably placed a crown stone at this location (not a mile point divisible by 5) because it represented the north end of the Tangent Line and south end of the Arc Line.
During boundary re-surveys in 1961-62 by the US Coast & Geodetic Survey (USC&GS) and in 1975-1977 by its successor, the National Geodetic Survey (NGS), five Mason-Dixon stones were repositioned to the original (but re-calculated) boundary line. The five were the markers at Miles 34, 45, 63, 73 and 75. Also, fifteen stones were found to be “missing”; of these, eleven were restored. A few of the surviving markers (two or three) have been moved short distances along the line to distance them from roads, plowing operations and other hazards.
According to the 1994 boundary agreement between Delaware and Maryland, the surviving Mason-Dixon and Graham Survey stones continue to mark this portion of the two states’ common boundary line.
References:
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)
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 (
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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 (
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Shenck, William S., “Delaware’s State Boundaries” (Delaware Geological Survey, undated) at (
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Wikipedia article: “Mason-Dixon line” at (
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Miscellaneous National Geodetic Survey datasheets and state historical signs
Also, the “State Boundaries” section of the Delaware Geological Survey (DGS) website at (
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