USCGS 12-Mile Circle Mile 17, 1892, DE-PA, is a dressed, gray gneiss frustum set by the US Coast & Geodetic Survey (USCGS) under the supervision of W. C. Hodgkins to demarcate the boundary between New Castle County, DE and Delaware County, PA. It is one of 46 such stones set by the USCGS to mark the 22.6-mile arc that forms Delaware’s northern boundary. That arc is a compound circle (originally meant to be centered on the courthouse at Newcastle, DE) with a radius of about 12 miles. The stone is in both the NGS and Geocaching databases as station BOUNDARY MIONUMENT 17 DE PA, PID = JU3627: (
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The stone is about 12 inches square at the bottom, about 10 inches square at the top, and it projects about 28 inches. A “D” is cut into the south face, a “P” is cut into the north face, “17” is cut into the west face, and “1892” is cut into the east face. Additionally, a line, corresponding to the boundary line, is scribed across the top of the stone. The stone is in excellent shape with no apparent damage and little apparent weathering. It is one of the best and most accessible examples of the 1892 survey stones.
The stone is located about seven miles north-northeast of downtown Wilmington, DE, (although still within the city limits), and in the lawn immediately west of the historic Ebright House. The Ebright House, an old, gray stone, two-story house now serves as the management office for a mobile home park. The location is private property but there is little problem with accessibility. Both the stone and Ebright House stand along the south side of Winterset Road, which serves as the main entrance drive to the mobile home park.
The stone is 141.7 feet east of triangulation station EBRIGHT (PID = JU3626). Unfortunately, the location of EBRIGHT is a now a parking area, and the disk has been paved over. The stone is also about 35 feet southeast of EBRIGHT Reference Mark No. 1, about 35 feet south of the centerline of Winterset Road, about 16 feet west-northwest of the west door of the Ebright House, 15 feet north of the north edge of the visitors’ parking spaces, and 5.5 feet west of the west edge of a concrete sidewalk.
The stone also stands about 975 feet northwest of the azimuth mark for EBRIGHT. The azimuth mark, located along the west side of Ebright Road, has the distinction of being at the highest point in Delaware: 442 feet.
To reach from Exit 8 off Interstate Highway 95 just north of downtown Wilmington, DE, go north on US Highway 202 (Concord Pike) for about 5.5 miles to the intersection with DE State Highway 92 (Naamans Road). Turn right and go east on DE State Highway 92 for about 1.05 miles to the intersection with Ebright Road. Turn left and go north on Ebright Road for about 0.66 miles to the state line and the intersection with Winterset Road. Turn left and go west on Winterset Road for about 0.17 miles to a driveway on the left, about 100 feet west of the Ebright House. Turn left into the parking area and park immediately southwest of the Ebright House. The stone will be in front of you in the lawn.
HISTORY OF THE TWELVE-MILE CIRCLE BOUNDARY AND THE WEDGE
The Twelve-Mile Circle is a 22.57-mile compound circle that forms Delaware’s northern boundary with Pennsylvania. In 1892 - 1893, it was marked with 46 stones; 41 of the historical stones survive.
In 1681, Charles II granted William Penn all the land west of the Delaware River between the 40th and 43rd Parallels, excluding the land within a twelve mile circle around New Castle. Accurate information about the colonies’ geography was imperfect - the 40th Parallel is about 23.5 miles north of New Castle. New Castle was located in lands (roughly, modern Delaware) under the control of the Duke of York (later, King James II). That same year, Penn, seeking better access to the sea for Pennsylvania, leased from the Duke the lands that lay between New Castle and Cape Henlopen. At the time, the exact location of Cape Henlopen was not known with certainty. Shortly thereafter, the Duke of York conveyed the Delaware colony to Penn. The Duke had previously divided the colony into three counties. Penn retained the division but renamed the counties as New Castle, Kent and Sussex. Penn annexed the Delaware colony to his larger holding, Pennsylvania, and referred to Delaware thereafter as the “Three Lower Counties”. In 1683, the Penn and Calvert families began negotiating the precise boundaries between their respective interests. Those negotiations failed and, in 1685, the Committee for Trade and Plantations ruled that the boundary between Maryland and the Three Lower Counties colonies would be a line that ran northerly from the middle of the Delmarva Peninsula to a point tangent with the Twelve Mile Circle around New Castle.
In 1700, Penn granted the Three Lower Counties their own legislature. In 1701, he commissioned two surveyors, Thomas Pierson and Isaac Taylor, to survey and mark the Twelve Mile Circle boundary. The surveyors centered their survey on the approximate center of the town boundaries of New Castle, and marked their line with tree blazes (which did not survive with any reliability).
In 1750, after years of additional negotiations and legal actions, the Court of Chancery appointed commissioners to survey the boundaries between the Penns’ and Calverts’ respective holdings. In 1750 - 1751, colonial surveyors ran a line across the Delmarva Peninsula and established the Middle Point, or southwest corner of Delaware. In 1760, the Court validated the parties’ Final Agreement concerning the boundaries. The agreement incorporated the Court’s 1750 ruling and several additional clarifications. The clarifications included (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” (as established in 1751) of the Transpeninsular Line that ran west from Fenwick Island on the Atlantic coast across the Delmarva Peninsula to the eastern shore of the Chesapeake Bay,
c. The western boundary of Delaware was to be a line (the “Tangent Line”) run northerly from the Middle Point to a point tangent with the Twelve Mile Circle (the “Tangent Point”),
d. The Tangent Line was to be run due north (the “North Line”) from the Tangent Point until it intersected a parallel of latitude (the “West Line”) that ran east-west through a point fifteen miles south of the most southerly point in Philadelphia,
e. Furthermore, 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,
f. The West Line, constituting the northern boundary line of Maryland with Pennsylvania, was to be a parallel of latitude that ran through a point fifteen miles south of the most southern point in Philadelphia, and was to extend westward from its intersection with the North Line to a point five degrees of longitude west of the Delaware River.
In 1763, the proprietors of Pennsylvania (and Delaware) and Maryland engaged Charles Mason and Jeremiah Dixon to run and mark the boundary lines between the three colonies in accordance with the Court of Chancery’s findings. In 1764, Mason and Dixon established the location of the line of constant latitude 15 miles south of Philadelphia and the initial point for the West Line ( and marked it with the “Post Mark’d West”). Also, in 1764, they ran the Tangent Line from the southwest corner of Delaware to the Tangent Point on the Twelve Mile Circle. During the period 1764 - 1767, they ran the West Line for about 233 miles from the Post Mark’d West. In 1765, they also established the Arc Line and the North Line. The Arc Line ran along the Twelve Mile Circle for about 1.47 miles, and the North Line ran due north for about 3.6 miles to the West Line. The North Line intersected the West Line about three miles west of the Post Mark’d West, and the intersection established the northeast corner of Maryland.
Since the West Line ran north of the western-most point of the Twelve Mile Circle and its eastern terminus was located nearly due north of the western-most point of the Circle, a southward-pointing “Wedge” of territory was formed by the boundaries. From the intersection of the North Line and the Circle, the North Line ran due north, and the Circle ran northeast. The resulting Wedge was 3.574 miles along its north-south side, 0.789 mile across at the top, and was completed by a 3.674-mile segment of the Circle. Both Pennsylvania and Delaware claimed the odd-shaped 683 acres.
In 1849, a joint boundary commission engaged Lt. Col. J. D. Graham of the US Corps of Topographical Engineers (USCTE, later incorporated into the US Army Corps of Engineers) to re-survey the North and Arc Lines. Graham validated Mason and Dixon’s survey of the relevant line segments with a few minor adjustments, and set a three-sided stone at the intersection of the North Line and the Circle, affirming Pennsylvania’s claim to the Wedge. Delaware protested the result.
In 1889, the two states agreed that the Wedge belonged to Delaware and, in 1892, a joint boundary commission engaged W. C. Hodgkins of the US Coast and Geodetic Survey (USCGS, now the National Geodetic Survey) to re-survey the circular boundary. Hodgkins extended the West Line eastward (for about 0.789 miles) to a point exactly 12 miles from the New Castle courthouse (the point is now known as the “Arc Corner”). From the Arc Corner, Hodgkins surveyed and marked the remaining 22.57 miles to the Delaware River. Under prevailing boundary principles (a line in use is more valid than a line defined on paper), Hodgkins preserved the few surviving 1701 boundary points (none of which was exactly 12 miles from the New Castle courthouse). The resultant line is a compound circle. From the Arc Corner, the Circle runs northeasterly for about 10.9 miles with a radius of about 11.58 miles. The line then runs easterly to the Delaware River for about 11.7 miles with a radius of about 12.81 miles. Neither of the two radii is centered on the New Castle courthouse.
Hodgkins’ extension of the West Line eastward created a line segment known as the “Top of the Wedge Line”, and his newly-surveyed circle created a thin strip of disputed territory (known as the “Horn”) immediately northwest of the line. Delaware and Pennsylvania agreed that the Wedge belonged to Delaware and the Horn belonged to Pennsylvania. The US Congress ratified the result in 1921.
By extending the West Line eastward, Hodgkins changed the intersection of the North and West Lines from the MD-PA boundary intersection point to a MD-DE-PA tri-state intersection point. The point is called the MDP Corner today, and is marked with an 1849 USCTE granite stone at PID = JU3841.
The Twelve Mile Circle was originally marked with 46 stones at one-half mile intervals. The southwestern-most stone is at the intersection of the (eastward) extended West Line and the Twelve Mile Circle and is marked with a Brandywine Granite frustum (truncated obelisk), 14 inches square at the bottom and 12 inches square at the top, that projects about four and one-half five feet, and is at PID = JU3827 (BOUNDARY INIT PT DE MD PA = ARC CORNER). A similar stone stands at the eastern end of the Circle: it is known as the “Terminal Monument”, and supports triangulation station MARCUS at PID = JU3326. The stones along the Circle that mark whole miles are 12 inches square at the bottom, 10 inches square at the top, and project from 0 to 30 inches. Each is marked with a “D” cut into the south or southeast face, a “P” cut into the north or northwest face, the mile number (e.g.“17”) cut into the west or southwest face, and “1892” cut into the east or northeast face. Additionally, each has a line, corresponding to the boundary line, scribed across the top of the stone. The stones that mark the mid-points between each mile marker are the same size as the mile markers and “1/2” is inscribed on the west face of each. All the stones except the stone at ARC CORNER are white gneiss from Chester, PA.
Hodgkins completed field work in November, 1892, and set the initial and terminal monuments in December. A contractor set the remaining 44 stones in April, 1893.
The stones that no longer survive once marked the 1.5, 3.5, 6.5, 13.5 and 20.5 mile points from the stone at the Arc Corner.
According to the 1993 boundary agreement between Delaware and Pennsylvania, the surviving 1892 USCGS Survey stones continue to mark this portion of the states’ common boundary line.
References:
Bayliff, William H., “The Maryland-Pennsylvania and Maryland-Delaware Boundaries”, (Maryland Board of Natural Resources, Bulletin 4 Second Edition, 1959);
Danson, Edwin “Drawing the Line: How Mason and Dixon Surveyed the Most Famous Border in America” (John Wiley & Sons, 2001);
Hodgkins, W.C., Appendix No. 8-1893 (in two parts), “Part I. - A Historical Account of the Boundary Line Between the States of Pennsylvania and Delaware” and “Part II. – Detailed Account of the Work on the Pennsylvania – Delaware Boundary Line Executed by W. C. Hodgkins, Assistant”, Report of the Superintendent of the U. S. Coast and Geodetic Survey for the Fiscal Year Ending June 30, 1893, (Washington, DC, Government Printing Office, 1895)
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);
Shenck, William S., “Delaware’s State Boundaries” (Delaware Geological Survey, undated) at (
visit link) ;
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.