MASDIX Arc Line Mile 83, 1766, DE-MD, is a 12-inch by 12-inch Portland Stone (oolitic limestone) shaft that projects 15 inches. It was set by Charles Mason and Jeremiah Dixon in 1766 to demarcate their 1765 survey of the Arc Line. It is located in a split-rail pole enclosure in a fallow field on the Stine-Haskell Research Labs facility (a subsidiary of DuPont). About 2.3 miles southwest of Newark, DE, and on the New Castle County, DE, – Cecil County, MD, boundary line. It is 83 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 83 DE MD at PID = JU3850: (
visit link) and (
visit link) . On USGS topographic charts it is identified as “Arc Stone 4”.
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 is erect and stable, and is in good condition. The cut "M" and cut "P" are both very crisp, and much of the fluting is visible.
Mason and Dixon first surveyed this position on or about June 5, 1765, and finalized the position on or about November 4, 1766. The stone was set on or about November 4, 1766 under their direct supervision. The US Coast and Geodetic Survey monumented the stone in 1961 as BOUNDARY MONUMENT 83 DEL MD.
To reach from Exit 109 off Interstate Highway 95 south of Newark, DE, go northeast on Maryland State Highway 279 (Elkton Road) for about 1.0 miles to the state boundary line. Continue northeast, now on Delaware State Highway 2 (Elkton Road) for about 0.6 miles to the Stine-Haskell main gate on the left. From there (and, assuming you have arranged access ahead of time), security personnel will escort you to the stone.
HISTORY OF THE ARC LINE
The Arc Line forms a small portion of the boundary line between Delaware and Maryland. It is a 1.47-mile segment of the Twelve Mile Circle boundary line centered on the courthouse at New Castle, DE. It extends north and south from the western-most point of the Circle, and is marked with nine surviving historical stones that are described below.
In 1760, after 80 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 ratified a Final Agreement between the parties regarding the boundaries of those three colonies. Among the Court’s determinations were (paraphrased):
a. The Twelve Mile Circle forming the northern boundary line of Delaware with Pennsylvania was to be centered on the cupola of the New Castle courthouse and measured horizontally as a radius,
b. The southwest corner of Delaware was to be the “Middle Point” of a line to be run from Cape Henlopen on the Atlantic coast (the modern Fenwick Island) across the Delmarva Peninsula,
c. 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,
d. The Tangent Line was to be run due north (the “North Line”) from the Tangent Point until it intersected a line of constant latitude (the “West Line”) fifteen miles south of the most southerly point in Philadelphia,
e. If any portion of the Twelve Mile Circle extended west beyond the North Line, the area within the Circle would remain Delaware territory (it did, and the portion of the colony’s boundary that the extending Circle formed would later be known as the “Arc Line”), and,
Prior to its 1760 ruling, the Court had appointed local surveyors to run the Trans- peninsular Line and, then, to run the Tangent Line northerly to the Twelve-Mile Circle boundary line. In 1750-1751, the surveyors ran and marked the Transpeninsular Line. In 1761, the surveyors began to run the Tangent Line 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 complete this line, and to survey and mark all the boundary lines between Maryland and the Penns’ two colonies.
In 1764, Mason and Dixon accepted the colonial surveyors’ determinations of the Middle Point and the Tangent Point and ran the Tangent Line. In June, 1765, Mason and Dixon ran a line due north from the Tangent Point and established both the Arc Line and the North Line segments of the Delaware-Maryland boundary line. That month, they also marked the Arc Line with five unmarked dark gray gneiss stones (one at the Tangent Point and four in the “periphery” of the Circle. In November, 1766, they added a standard limestone intermediate mile stone that served to mark the 83rd mile north of the southwest corner of Delaware.
In 1849, Lt. Col. J. D. Graham, US Corps of Topographical Engineers (USCTE), re-surveyed the Arc Line and the North Line. The USCTE survey set new stones at the north and south ends of the Arc Line, and an additional stone on the line about 0.7 miles north of the Tangent Point.
According to my calculations, the Arc Line is 1.467 miles long with a chord of 1.466 miles. At its widest, the sliver of land between the Arc Line and an imaginary line run due north from the Tangent Point is 118.3 feet. The area gained by Delaware from the specification that created the Arc Line is 14.01 acres.
The Arc Line was marked with nine historical stones, all of which survive:
1. The “Tangent Stone”, a granite 1849 US Corps of Topographical Engineers (USCTE) survey stone with PID = JU3840 (BOUNDARY MON 82 TANGENT STONE).
2. Abutting the Tangent Stone is roughly-dressed gneiss stone set by Mason and Dixon in June, 1765. This stone does not have a PID.
3. About 0.4 miles north of the Tangent Stone, a stone with PID = JU4144, (BOUNDARY ARC STONE 1 DE MD RESET) originally set by Mason and Dixon in June, 1765. This stone lies in a chamber below the southwest-bound lanes of MD State Highway 279 / DE State Highway 2 (Elkton Road). The DGS describes the stone as an unmarked, obelisk-shaped piece of granite.
4. About 0.7 miles north of the Tangent Stone, a roughly-dressed gneiss stone with PID = JU3851 (BOUNDARY ARC STONE 2 DE MD) set by Mason and Dixon in June, 1765. It is a 7 x 12 x 20-inch, unmarked gneiss stone of the same type as the stone that abuts the Tangent Stone.
5. About 0.7 miles north of the Tangent Stone (and about 41 feet north of ARC STONE 2), a granite 1849 USCTE granite stone with PID = JU3852 (BOUNDARY ARC STONE 3 DE-MD).
6. About 1.0 miles north of the Tangent Stone, a dressed stone with PID = JU3850 (BOUNDARY ARC STONE 4, BOUNDARY MONUMENT 83). It is an intermediate mile marker set by Mason and Dixon in November, 1766. It is a 12-inch by 12-inch Portland Stone shaft that projects about 15 inches, and has a cut “M” on the west face and a cut “P” on the east face.
7. About 1.1 miles north of the Tangent Stone, an unmarked stone with PID = JU3849 (BOUNDARY ARC STONE 5 DE MD) set by Mason and Dixon in June, 1765.
8. About 1.4 miles north of the Tangent Stone, a stone with PID = JU3846 (MD SEL BDRY INTERSEC STONE 2). It is an 1849 USCTE stone, and is known locally as the “Prism Stone”. It is a three-sided granite shaft that projects about 24 inches. It has a cut “D” on the southeast face, a cut “M” on the west face, and a cut “P” on the north face.
9. At the Prism Stone, a roughly-dressed stone with no PID, but identified by the Delaware Geological Survey as the stone that Mason and Dixon set on this spot in June, 1765. It is an 8 x 12 x 44 dark gray gneiss stone, and is lying on its side in a wood cradle a few feet from the Prism Stone. It is of the same shape and material as Arc Stone 2.
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 (
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 (
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Shenck, William S., “Delaware’s State Boundaries” (Delaware Geological Survey, undated) at (
visit link) ;
Wikipedia articles:
“Mason-Dixon line” at (
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“The Wedge (border)” at (
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“Transpeninsular Line” at (
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“The Twelve Mile Circle” 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 (
visit link) has several valuable references: Shenck, 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.