Today there is no common border between Virginia and Pennsylvania - but between 1681 and 1863, the southwestern border of Pennsylvania was shared with Virginia. Exactly what territory was Virginia and what was Pennsylvania... well, that was a challenge that took about 100 years to resolve.
In 1681, the western boundary of Pennsylvania was established in William Penn's charter - "The said Lands to extend westwards five degrees in longitude, to bee computed from the said Easterne Bounds..."1 William Penn was determined to acquire the Native American claims to the land by legitimate negotiations and purchases, but his efforts to negotiate with fellow Europeans claiming land in North America may have been more difficult.
The fundamental problem with Penn's charter is that the point of beginning for his southeastern boundary... did not exist. Penn's charter started with the intersection of a circle 12 miles from New Castle (now located in Delaware) and the beginning of the 40th degree of latitude, "on the South by a Circle drawne at twelve miles distance from New Castle Northward and Westward unto the beginning of the fortieth degree of Northern Latitude." However, the 40th degree is so far north of New Castle that the lines never intersect, so the 1681 charter created great confusion between the Calverts of Maryland and the Penns of Pennsylvania.
Some Pennsylvania officials even claimed that the "beginning" of the 40th degree of latitude was the 39th parallel, and all the land north of the 39th degree of latitude was included in Penn's grant.3 A degree of latitude is roughly 69 miles (on land), so a lot of territory was at stake. Until Penn's claimed eastern and southern boundaries of the colony were defined, it was impossible to establish the southwestern corner, 5 degrees of longitude to the west of the southeastern corner.
In addition, the French did not accept Penn's western land claims. England and France had been rivals for settlement and the fur trade of North America since the start of the 17th Century. In 1748, the Treaty of Aix-la-Chapelle settled one of the many French/English conflicts in Europe (the War of Austrian Succession, known in North America as King George's War). However, the negotiators failed to resolve the claims of Virginia to lands that the French also claimed in North America - North America was a sideshow then, not the main event.
Before and after the Treaty of Aix-la-Chapelle, French-English competition extended inland from the fishing fleets off Newfoundland to the Ohio River Valley. The Treaty of Aix-la-Chapelle negotiators in Europe had even restored the fortress of Louisbourg (on Cape Breton Island in Nova Scotia) to France. The colonists had captured Louisbourg, with assistance from the British Royal Navy. This was a big deal in North America, because it gave the English control over the valuable fishing grounds offshore of Newfoundland.
In the 1740's, the French decided to link their outposts along the Great Lakes to their colonies at the mouth of the Mississippi River. European explorers were just beginning to penetrate the Shenandoah Valley. Captain Bienville de Celeron canoed from Montreal down the Ohio River in 1749, buring lead plates on the Ohio at various confluences with major creeks and shouting "Vive le Roi" to establish the claim of the King of France to the Ohio River watershed. Perhaps more importantly, de Celeron chased British traders away from Native American villages.4
The French planned to build a series of forts along the Ohio River, extending supply lines from Quebec/Montreal on the Saint Lawrence River. This would link the French settlements in Canada with those in Louisiana and isolate the English colonies along the Atlantic Ocean, blocking European rivals from expanding their North American colonies west into the Mississippi/Ohio River watersheds.
The French plans were triggered in part by plans of Virginians to expand into the same region. In particular, in 1749 the king of Englant granted the Ohio Company (including Governor Dinwiddie) up to 500,000 acres west of the Allegheny Mountains. Under the terms of the initial grant, in exchange for settling 100 families and building a fort within seven years, the company would earn its first 200,000 acres. In preparation, it established its field headquarters at Wills Creek, now Cumberland (Maryland).
Partly to counter the French claims, Joshua Fry and Peter Jefferson (Thomas Jefferson's father) produced a map of Virginia in the early 1750's showing Virginia's boundaries included the land where the Allegheny and Monongahela rivers join (where Pittsburgh is now located). Other maps based on the Fry-Jefferson cartography repeated the claim. Viewed from Williamsburg, the Ohio River was in Virginia - and not Pennsylvania.
Fry-Jefferson map showing western Pennsylvania border located far to the east of the final boundary line
"A map of the most inhabited part of Virginia containing the whole province of Maryland with part of Pensilvania, New Jersey and North Carolina. Drawn by Joshua Fry & Peter Jefferson in 1751."
Source: Library of Congress
1770 map showing Pittsburgh (Fort Duquesne) located in Virginia
Source: Library of Congress - John Henry, A new and accurate map of Virginia wherein most of the counties are laid down from actual surveys.
With a concise account of the number of inhabitants, the trade, soil, and produce of that Province
John Mitchell produced a separate map between 1755-61. It suggested the Forks of the Ohio, including the site of modern-day Pittsburgh that the French called "Fort duQuesne," was located in Pennsylvania:
The Virginia claim to the confluence of the Allegheny and Monongahela rivers (the "Forks of the Ohio River") was the Third Charter granted by King James I in 1612, plus the 1744 Treaty of Lancaster with the Iroquois. During the treaty negotiations, the Iroquois claimed ownership of the lands west of the Allegheny Mountains by right of conquest:
The Virginians claimed to have purchased those Iroquois rights in 1744, so the officials in Williamsburg were willing to assert ownership through right of conquest, though initial settlement, and through a royal grant. The French, of course, did not feel obliged to honor any English claims. French military expansion into the Ohio River Valley would block any English colony's claim to the land, and ensure continued French control over trade with the Native Americans.
The pacifist Quakers in the Pennsylvania legislature were unwilling to raise taxes to confront and potentially fight the French... but the Virginians were willing to assert their land claims. In late 1753, Governor Dinwiddie sent an emissary (an ambitious young man named George Washington...) to tell the French to abandon their plans to build a string of new forts from Lake Erie down into the Ohio River valley. Washington carried a specific message from the English governor of the Virginia colony to the French:7
Washington reached Fort Le Boeuf, in the Ohio River watershed near Lake Erie, and was well treated by the French officers led by Legardeur de St. Pierre. The French officials in the middle of nowhere must have been entertained by the company of a young, well-spoken representative from Jamestown in the middle of winter - but they rejected all English claims to the Ohio River. In 1754, the French continued to march downstream. At the Forks of the Ohio they ejected the Virginia settlers trying to build Fort Prince George and instead established the French Fort Duquesne.
Later in 1754, Joshua Fry led the Virginia Regiment on a military expedition to the forks to protect the Virginians and establish an English presence at that strategic location. However, Fry died after falling off his horse, and young George Washington assumed command of the Virginia Regiment. He led the colonial military expedition into major failure, both militarily and diplomatically.
Washington attacked a French unit encamped in a Pennsylvania valley (now called Jumonville Glen), away from Fort Duquesne. After the attack, in which the Virginians were successful at killing nearly all the French, including their leader Joseph Coulon de Villiers de Jumonville, Washington retreated to Great Meadows. There he stopped, and erected his own defensive "Fort Necessity." It was a poor tactical decision to stop rather than to keep retreating. After the French and their Indian allies attacked the fort, Washington had to surrender it. As part of the surrender, he signed a document in French (a language he did not read...) that said he had assassinated de Jumonville.
This incident helped to trigger the French and Indian War (or the Seven Years War, as it was known in Europe). The war was an imperial conflict that stretched from India to the Caribbean - and north to Canada. In 1755, the English sent two regiments across the Atlantic Ocean, led by General Braddock. His expedition was defeated by the French and Indians on the outskirts of Fort Duquesne, in a battle in which both Braddock and the opportunity for Virginia to control the Forks of the Ohio both died.
In 1758, the British under John Forbes finally captured Fort Duquesne, renaming it Fort Pitt. Much to the frustration of the Ohio Company and other land speculators in Virginia, Forbes' army in 1758 had been organized in Pennsylvania. His march westward across the colony established good roads that connected Philadelphia to the Ohio River with a shorter, better road than the route from Virginia that General Braddock used. As Forbes reported back to London:8
Trade between Philadellphia and Pittsburgh undercut the Virginia colony's economic links up the Potomac River to the Ohio, and ultimately led to Virginia accepting the Pennsylvania claim to much of the Allegheny and Monogahela river valleys.
In the 1763 Treaty of Paris, the French surrendered their claims to land along the Ohio River. Virginia officials continued to assert their land claims, and even included southeastern Pennsylvania within the boundaries of three Virginia counties in 1776, but in 1763-7 a survey by two Englishmen would become the basis for locating the line that we recognize today as the southern boundary of Pennsylvania.
Lewis Evans map showing Mason-Dixon line extended as the western Virginia/Pennsylvania border,
"A general map of the middle British colonies in America, viz. Virginia, Maryland, Delaware, Pensilvania, New-Jersey, New York, Connecticut & Rhode-Island: Of Aquanishuonigy the country of the confederate Indians comprehending Aquanishuonigy proper, their places of residence, Ohio & Thuchsochruntie their deer hunting countries, Couchsachrage & Skaniadarade their beaver hunting countries, of the Lakes Erie, Ontario and Champlain. Wherein is also shewn the antient & present seats of the Indian nations."
Source: Library of Congress
Ever since the proprietary grant to William Penn in 1681, the border between Virginia and Pennsylvania had depended upon defining the eastern edge of Pennsylvania. Once that eastern edge of Pennsylvania was resolved, surveyors could locate a north-south line "five degrees in longitude, to bee computed from the said Easterne Bounds..." to mark the western edge of Pennslvania. Until then, land speculators in Pennsylvania chartered the Indiana Company, while Maryland speculators formed the Illinois and Wabash companies, and sought rights to the same lands being claimed by the Virginia-based Ohio Company.
The confusion was created because the colonial charters for Pennsylvania and Maryland granted the same land around the 40th degree of latitude to both colonies. Finally, the Calverts of Maryland and the Penns of Pennsylvania hired Charles Mason and Jeremiah Dixon ("neutral" surveyors from England) to survey the southern boundary of Pennsylvania/northern boundary of Maryland. Mason and Dixon spent four years (1763-1767) marking the location of the colonial boundaries with monuments on the ground. They started by marking a spot 15 miles south of Philadelphia, a "point of beginning" previously accepted by Penns and Calverts as the appropriate dividing line. From that marker, Mason and Dixon surveyed east to Delaware and then south to define the Delaware/Pennsylvania border.
After Mason and Dixon started surveying west of the marker defined as the point of beginning, they finally reached a point due north of the headwaters of the Potomac River. At that point, the surveyors began defining the boundary between Virginia-Pennsylvania. Maryland's western border was the "headspring" of the Potomac, so its western boundary was defined by a line between that natural feature (marked by the Fairfax Stone in 1746) and the Mason-Dixon line. West of the headspring and south of the Mason-Dixon line was the colony of Virginia.
However, due to hostility of the Native Americans in the mountains, Mason and Dixon were unable to complete their east-west line and determine the southwestern corner of Pennsylvania. Their survey stopped on October 9, 1767, 233 miles west of the point of beginning, 30 miles west (and north...) of the "head spring" of the Potomac River, and 36 miles east of the line that would be "five degrees in longitude... computed from the said Easterne Bounds." That left enough confusion for pushy, land-savvy Virginans to sell property that may, or may not, be located in Virginia.
Pennsylvania claimed the same area as Virginia, and created Westmoreland County in the southwestern corner of Pennsylvania. Beginning in 1771, settlers loyal to Pennsylvania dealt with local officials appointed by the Pennsylvania General Assembly, or elected locally in Pennsylvania-sponsored elections, for legal and political decisions. Beginjing in 1775, settlers loyal to Virginia living in the area had the opyion of relying upon a separate, parallel system of local officials for taxes, elections, and lawsuits.
In early 1775 Dunmore issued a proclamation affirming the Virginia claim to the territory, which the General Assembly designated as the District of West Augusta. Dunmore appointed Dr. John Connolly as local captain of the Virginia militia in Pittsburg. Connolly was agressive in asserting his authority (and later, when the American Revolution started, his support for King George III...). Westmoreland County (PA) officials arrested Connolly, and in turn he arrested Pennsylvania officials who exercised their authority. In 1776, Virginia formally created three separate counties from the District of West Augusta - Yohogania, Monongalia, and Ohio.
Overlapping jurisdiction meant that property rights were very, very confused. One option proposed for resolving the territorial dispute was to create a new state of Westsylvania. The continuing conflict among states supposedly united to fight the British during the Revolutionary War was a concern to the Continental Congress, as was the difficulty created in managing relations with Native American tribes on the frontier. In 1780, the Congress convinced both Virginia and Pennsylvania to settle their dispute by completing the surveys of Pennsylvania's southwestern and western boundary lines. The states agreed that the line would start at the Delaware River and go 5 degrees west from that point.
Commissioners were appointed by the legislatures of Virginia and Pennsylvania to define the boundary between Virginia and Pennsylvania, and the last miles of the Mason-Dixon line were surveyed initially by Alexander McClean of Pennsylvania and Joseph Neville of Virginia in 1782. The boundaries of Monongalia and Ohio counties were changed, excluding those portions that were inside Pennsylvania. Yohogania County, Virginia, was completely eliminated, with the small portion outside of Pennsylvania being transferred to Ohio County - and its court records transferred to Westmoreland County, Pennsylvania.10
A permanent survey was finalized in 1784-86, extending the line north from Pennsylvania's southwestern corner to the Ohio River. By the time the western edge of Pennsylvania, "five degrees in longitude... from the said Easterne Bounds" was finally surveyed, the Continental Congress had passed the Land Ordinance of 1785, which defined how the lands across the Ohio would be surveyed and sold to settlers in an orderly process where boundary surveys would be completed before the government's land would be sold.
The Pennsylvania-Virginia border lasted until 1863, when the western counties of Virginia became the separate state of West Virginia.