Post Mark’d West, 1952, DE, is a granite shaft located in the Possum Hill section of White Clay Creek State Park, New Castle County, DE. It commemorates the initial point established by Charles Mason and Jeremiah Dixon on June 12, 1764, for their survey of the PA-MD boundary line. The monument is a seven-inch by seven-inch granite shaft with a pyramidal top that projects 32 inches, and is enclosed by a low, wood and pipe fence. The west face is inscribed “WEST”, the north face “This post used as base point in the survey of the Mason-Dixon Line 1763 – 1767”, the east face “Site of Post Mark’d West set up by Mason and Dixon June 12, 1764”, and the south face is blank. The original post was wood, painted white with “West” carved into the west face. It stood on land owned at the time by Mr. Alexander Bryan. This commemorative marker was donated by Mr. S. Hallock du Pont in 1952 (he owned the land at the time). Today, the land is owned by the State of Delaware.
To reach from Exit 1 off Interstate 95 south of Newark, DE, go north on State Route 896 (aka South College Ave) for about 3.1 miles to the intersection with State Route 273 eastbound in downtown Newark. Turn right and go east on State Route 273 for about 0.45 miles to the intersection with North Chapel Street. Turn left and go northerly on North Chapel Street (which turns into Curtis Mill Road and Paper Mill Road) for about 3.7 miles to the intersection with Smith Hill Road leading west. Turn left and go west on Smith Mill Road for about 0.3 miles to an unpaved parking area on the south side of the road. From the parking area, take a distinct trail south-southwest for 0.20 miles to a fork. Take the left fork and go southeast and east for 0.40 miles to a large deadfall tree on the left and a sign post that indicates “Mason-Dixon Monument”. Walk south for about 100 yards to a clearing and the monument. CAUTION: This monument and the trails leading to it lie in an area that is actively hunted from September through early February. Call the park office at 1-302-368-6900 to confirm that the trails are open to non-hunters before attempting to visit this monument.
HISTORY OF THE WEST LINE
The West Line is the southern boundary of Pennsylvania. It is a line of constant latitude that extends from an intersection with the Twelve Mile Circle boundary of Delaware (about 2.8 miles north-northwest of Newark, DE) westward for about 252.7 miles to the southwest corner of Pennsylvania (about 30 miles northwest of Morgantown, WV). In 1766 and 1767, Mason and Dixon marked the first 132 miles (starting at the east end of the line) with stones. Beyond the 132 mile point, they used cairns and posts to mark the miles to the limit of their survey (about 231 miles). Subsequent surveys, most notably in 1901-1903, added stone markers and replaced several of the original stones.
In 1632, Charles I of England granted George Calvert, the First Lord Baltimore, the land north of the Potomac River to the 40th Parallel. Calvert named the colony Maryland. In 1681, Charles II granted William Penn all the land west of the Delaware River between the 40th and 43rd Parallels, but excluding the land within a twelve mile circle around New Castle. [Apparently, accurate information about the colonies’ geography was a bit sketchy – the 40th Parallel is about 23.5 miles north of New Castle.]
By 1732, a large number of Pennsylvanians had settled on lands south of the 40th Parallel, and the Penn Family initiated negotiations to re-define the colony’s boundary line with Maryland. The negotiations failed and, in 1738, colonial surveyors ran a temporary boundary line 15 ½ miles south of Philadelphia on the east side of the Susquehanna River and 14 ¾ miles south of the city on the west side of the river. After protracted legal action, the Court of Chancery in 1760 ruled in favor of the Penns’ proposal to revise southward the boundary as originally described in the 1681 grant. The West Line, constituting the northern boundary line of Maryland with Pennsylvania, was to be a parallel of constant latitude fifteen miles south of the most southern point in Philadelphia, and was to extend from the northeast corner of Maryland (defined elsewhere) westward to a point equal to five degrees of longitude west of the Delaware River. By ruling that the line would be 15 miles south of Philadelphia, the Court relocated the boundary line about 19.16 miles south of the 40th Parallel. The Court of Chancery also appointed four colonial surveyors to survey and mark all the common boundary lines of Maryland, Pennsylvania and Delaware, but the task proved to be beyond the surveyors’ capabilities.
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 established the initial point for the West Line ( and marked it with the “Post Mark’d West”). The West Line started at a point where a line that ran due north from Delaware’s Twelve Mile Circle boundary (the “North Line”) intersected the line of constant latitude. This intersection stood about three miles west of the initial point at the Post Mark’d West. In 1765, Mason and Dixon surveyed the West Line to about 117 miles west of the Post Mark’d West (or, 114 miles west of the eastern end of the West Line). In 1766, they extended the West Line to about 165 miles from the initial point and, in 1767, they extended the line to about 234 miles west of the Post Mark’d West. They fell about 21 miles short of surveying the line for the full five degrees of latitude from the Delaware River. The colonial commissioners could not secure permission from the Native Americans who controlled the territory to continue.
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.
Mason and Dixon set a stone at the intersection of the North Line and West Line on June 18, 1765. In November, 1766, they set 64 limestone mile markers from Mile 1 through Mile 65 (leaving Mile 64 unmarked). In November and December, 1767, Richard Farrow, Mason and Dixon’s labor contractor, set 68 additional limestone markers from Mile 66 through Mile 132 (plus Mile 64). Jonathan Cope supervised the setting of the stones in 1767. In November, 1768, (about two months after Mason and Dixon left America) the joint boundary commissioners set a double crown stone at the northeast corner of Maryland
Along the West Line, the five-mile intervals are marked with stones that have the Penn and Calvert armorial crests on the north and south faces, respectively. The intermediate mile markers have a cut “P” on the north face and a cut “M” on the south. 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 and generally project about 30 – 36 inches. The vertical faces of the stones are fluted vertically (with very shallow flutes), with a two-inch band of horizontal fluting at the corners. 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.
Colonial surveyors John Leukens, John Ewing, David Rittenhouse, Thomas Hutchins and Andrew Ellicott completed the survey by determining the southwest corner of Pennsylvania in 1787.
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 a new, granite survey stone at the intersection of the North and West Lines; both the original Mason-Dixon stone and the 1768 double crown stone had disappeared in the early 1800’s. The USCTE stone is a 14-inch by 14-inch granite shaft that projects about 24 inches. It has an inscribed “P” on the north and east faces, and an inscribed “M” on the south and west faces. Additionally, “1849” is inscribed on the north face. It is in the NGS database at PID = JU3841 (BOUNDARY MON 87 DE MD PA = RM2).
In 1885, C. H. Sinclair of the US Coast & Geodetic Survey re-surveyed the Pennsylvania – West Virginia boundary line and set a stone on the boundary near the PA-WV-MD boundary intersection point.
In 1889, the Pennsylvania and Delaware agreed to a re-survey of and adjustment to their common boundary lines. In 1892, a joint boundary commission engaged W. C. Hodgkins of the US Coast and Geodetic Survey (USCGS, now the National Geodetic Survey) to conduct the survey. As part of the survey and boundary adjustment, Hodgkins extended the West Line eastward (for about 0.789 miles) until it intersected the Twelve Mile Circle boundary line centered on New Castle, Delaware. The extension of the West Line eastward created a line segment known as the “Top of the Wedge Line”. Both Delaware and 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 still marked with the 1849 USCTE granite stone at PID = JU3841. The intersection of the West Line and Twelve Mile Circle is marked with a gneiss 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).
Subsequent surveys, most notably in 1901-1903, added granite or marble markers (similar in design to the original Mason-Dixon stones) to the West Line, and replaced several original Mason-Dixon stones that had gone missing. In recent years, the Mason-Dixon Line Preservation Partnership and other professional surveying bodies have replaced several of the missing stones. In 2002 and 2003, they replaced missing original stones with granite crown stones at Mile 10 and Mile 75.
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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Robinson, Morgan, “Evolution of the Mason-Dixon Line” (The Journal of American History, 1909) at (
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Wikipedia article: “Mason-Dixon line” at (
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Miscellaneous National Geodetic Survey datasheets and state historical signs