Historical Markers
Mason-Dixon Line Historical Marker
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Mason-Dixon Line

Hershey/Gettysburg/Dutch Country Region


Marker Location:
Rt. 94 at state line, S of Pleasant Hill

Dedication Date:
May 27, 1970

Behind the Marker

Marking the border between Maryland and Pennsylvania, the Mason-Dixon Line, completed in 1765, ended an eighty-year dispute between Pennsylvania and Maryland.  The most famous border in the United States, the Mason-Dixon Line then became both a physical and symbolic boundary in the decades before the end of the American Civil War, dividing not only Pennsylvania from Maryland, but the North from the South; America as land of slavery and a land of freedom.  
Map of the Overlapping Claims of Maryland and Pennsylvania, and the Mason-Dixon...

The border dispute had its origins in 1681, when King Charles II extended the southern boundary of his land grant to William Penn to the fortieth parallel, the same line that King Charles I had set in 1632 as the northern boundary of the Maryland charter. Neither the royals nor the proprietors, however, knew exactly where that was, and both proprietors claimed the lands between the 39th and 40th parallels as their own.  Inaccurate maps, imprecise geodesic instruments, and flawed understanding of geography further complicated the situation.  The contested land claims resulted in both a loss of revenue for proprietors and difficulties for settlers, including fraudulent land sales and overlapping legal jurisdiction, law enforcement, and taxes.
Map of the Maryland-Pennsylvania boundary used as trial exhibits in the 1735...

In 1733 the tensions from mutual encroachment broke out into what became known as Cresap’s War, four-years of border skirmishes that began when Thomas Cresap and other Marylanders allegedly assaulted and harassed both Pennsylvania settlers and local Native Americans in retaliation for Pennsylvania settlers attempts to drive him off of his land.  In 1737 the two colonies ended the armed forays by deciding to let settlers determine which colony they wished to align themselves with. The next year, King George II ordered the survey of a temporary border that began 15 ¼ miles south of Philadelphia. 
Stone marker placed near Embreeville, PA, by Mason and Dixon in 1764 to conduct their survey.
Stargazers' Stone on the John Harlan or Stargazers' Farm, near Stargazers'...

This solution held until the early 1760s when colonial surveyors attempts to finalize an exact border broke down due to cost overruns and miscalculations as they attempted to “run lines.” So in 1763 the Penns and Calverts hired English astronomers and surveyors Charles Mason and Jeremiah Dixon to finish the work.  
On November 15, 1763, Mason and Dixon landed in Philadelphia with their books, charts, tables, and the best astronomical tools available. After receiving marker formal instructions from the commissioners from Pennsylvania and Maryland they began their work by determining the latitude of “the southernmost point of the city of Philadelphia.” 
On January 6, 1764 the surveyors placed their first mark at the south wall of the Plumstead and Huddle house on Cedar Street in Philadelphia (now 30 South Street) and from there proceeded exactly fifteen miles south, where they began establishing the boundary dividing Pennsylvania and Maryland.  Due south would have taken them across the Delaware River into New Jersey, so the following day, they instead traveled thirty miles west to establish a reference site on the same latitude as Cedar (South) Street.  There they encountered John Harlan’s farm where they established their headquarters and set up a mobile observatory. Calculating their position by the night sky, they then established the latitude and erected a stone marker (known as the “Stargazer’s Stone”) to mark the site. 
Page from the Journal of Charles Mason and Jeremiah Dixon, November 15, 1763....

In April, Mason and Dixon proceeded fifteen miles due south from Stargazer stone to the Alexander Bryan plantation, where they set their main reference point for the Pennsylvania-Maryland border and there erected an oak post with the word “West” carved into the west face. This “Post mark’d West,” as they called it, served as the “true latitude” reference point for the Pennsylvania-Maryland boundary line westward along the latitude of 39 degrees 43 minutes and 18 seconds. 

The survey team then traveled south to plot the boundary between Maryland and Delaware. Colonial surveyors already had established a temporary “Tangent (or Tangency) Line,” but Mason and Dixon had to resurvey and connect it with the 12-mile radius circle arc that formed the northern border of Delaware. Mason and Dixon spent most of 1764 surveying and placing mile stones along the now very clearly established 82 mile-long Tangent Line, then hunkered down for winter.
"A plan of the west line or parallel of latitude, which is the boundary...

In April of 1765, the surveyors started work on the Pennsylvania-Maryland border, at Bryan’s plantation. In late May the group reached the Susquehanna River – the place the commissioners designated as the finish line for their work-- then continued to survey the line into the fall.
"Position of the Democratic Party in 1852. 'Freemen of America, how...

Their work, however, was not done. In 1766 Mason and Dixon received new instructions to extend the “West Line” east to the Delaware River by the end of the year.; and in 1767 to west survey beyond the Allegheny Mountains. This last undertaking required delicate diplomacy on the part of British officials, who needed to secure permission of the Iroquois who claimed the land in question and commanded cooperation of other unfriendly tribes.  Fourteen Iroquois and translator Captain Hugh Crawford accompanied Mason and Dixon on their journey in 1767.  
Limestone marker placed by Mason and Dixon at the eastern edge of the boundary between Pennsylvania and Maryland.
Mason-Dixon Line Crownstone, Intersection of the Tangent Line and the Transpeninsular...

According to the diplomatic agreement between Iroquois and British diplomats, the Iroquois would ultimately decide where the survey ended. In July members of the Indian delegation and apprehensive laborers deserted after the group encountered an Iroquois war party headed south.

At Dunkard Creek (today just west of Route 79 in Greene County) the Iroquois contingent refused to permit Mason and Dixon to continue any farther.  On October 9, after close to four years of work, the survey ended, some 233 miles from “the Post mark’d West” and short of what is today Pennsylvania’s western boundary.  
In 1785 astronomer markerAndrew Ellicott, John Ewing, Thomas Hutchins, and markerDavid Rittenhouse would complete the line to Pennsylvania’s western border, some thirty-one miles beyond where Mason and Dixon had left off.
In the decades preceding the Civil War the Mason-Dixon Line took on a new meaning and ever growing significance as the legal and symbolic border between North and South. For enslaved African Americans heading north along the Underground Railroad crossing the Mason Dixon Line from Maryland into Pennsylvania marked their escape from slavery into freedom.
After the Thirteenth Amendment ended slavery in 1865, the Mason Dixon Line no longer represented the great divide between the two Americas. It remains, however, a symbol of the struggle for end of slavery in the United States and of the courage of the men and women who fled from slavery and those who assisted them.
A U.S. Coast and Geodetic Survey resurvey of the Mason-Dixon Line in 1901 and 1903 confirmed the accuracy of Mason and Dixon’s work. The Englishmen had never strayed further than 800 feet from the true line, and remained within an inch of accuracy in others. Today, many of the original marker stones remain visible, preserved by The Mason-Dixon Line Preservation Partnership.
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