War at the 40th Parallel:
How the Mason-Dixon Line was Created
"The 40th parallel is about where the Roosevelt Boulevard crosses the Schuylkill River at East Falls and runs west to the center of Lancaster today. Thus, in Chester County, anything south of Downingtown and Malvern would have been the property of Maryland from the viewpoint of Lord Baltimore’s family. This would have meant that the Penn’s dream of Philadelphia and ownership of any inhabited land in southern Pennsylvania would have been lost, so pressure was applied with varying degrees of success in London to resolve this land dispute."
- Mark Ashton, Chester County: A Modern History
Land Purchases 50 Years Apart Spark Conflict
In 1632, King Charles I granted Cecilius Calvert, Second Baron of Baltimore, the land that is known today as the state of Maryland:
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In the north, the grant began at the 40 degree north latitude line
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In the south by the Potomac River and the latitude through Watkins Point on the Eastern Shore
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In the east, the Atlantic Ocean
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In the west, by a meridian through the source of the Potomac River
In 1681, nearly 50 years after Calvert acquired Maryland, English Quaker William Penn was granted the land from King Charles II that became known as the Pennsylvania.
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In the north, Penn's land ended at the 43 degree north latitude line
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In the west, the land reached to a meridian five degrees west of the Delaware Bay
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In the east, the boundary was marked by the Delaware Bay.
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The southern boundary extended eastward along the 40th parallel of north latitude until it intersected an arc extending in a 12-mile radius from the courthouse in New Castle, which is now in Delaware.
The boundaries between Pennsylvania and Maryland did not meet each other. Instead, it created a wedge between them, causing a conflict between the Penn and Calvert families on who owned that wedge.
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1730 - Thomas Cresap Starts a War
Despite meeting with each other to find a compromise over the border between Pennsylvania and Maryland near the Susquehanna River, the conflict between the two families got worse. As more inhabitants settled into Pennsylvania and Maryland over time, ferries began to appear in two different states. In 1729, a Quaker named John Wright occupied a land at the Susquehanna River near Wrightsville, west of Lancaster, where he operated a ferry. One year later, Maryland's Thomas Cresap opened a ferry four miles south of Wright's ferry. Supporters of Wright's people found out about Cresap's Maryland connections, and began to attack him. Cresap swore out an arrest against the Pennsylvania mobs to a Pennsylvania magistrate, but his request was not warmly received. Thus, the Cresap’s War began that arose over disputes over who owned the land west of the Susquehanna. The Cresaps and their supporters would fight over who owned what is today Western Pennsylvania up to the time of the Revolution.
The Penns and Calverts Forge a Compromise
The battle over the Pennsylvania/Maryland border lasted more than 20 years until King George II brought about a cease-fire and created a truce between the Penns and Calvert families. In 1763, King George II dispatched Charles Mason and Jeremiah Dixon, both respected surveyors and astronomers of England, to the colonies to measure and mark a permanent border. This survey line 83 miles north – south and 233 miles east west is considered a milestone scientific achievement of the 18th century.
In Chester County, a Stargazer's stone was constructed by Mason and Dixon as a place to measure from using the stars while creating the boundaries between Pennsylvania, Maryland, and Delaware. The men would often stay at the nearby Harlan House near Embreeville in Newlin Township. The Harlan Family lived in that dwelling until 1956.
Bibliography
DeVan, Kathryn. "Our Most Famous Border: The Mason-Dixon Line." Pennsylvania Center for the Books. Last modified Fall 2008. https://pabook.libraries.psu.edu/literary-cultural-heritage-map-pa/feature-articles/our-most-famous-border-mason-dixon-line.