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VA/PA Boundary

The running of the Mason-Dixon Line, begun in 1763, effectively marked the southern limit of Pennsylvania, and the constitution of 1776 should have settled things permanently. But there was still some confusion about the southwest corner of PA the western border with VA (at least in the eyes of the VA General Assembly) and this corner was not agreed to until late 1784. ...
For some time, Augusta Co, then the West Augusta District, of Virginia, included some territory north of the Mason-Dixon, now included in Pennsylvania. In fact, the Augusta Co court sometimes met in what is Pittsburgh, today. In October 1776, the General Assembly defined the boundary between the county of Augusta and the District of West Augusta, and in the same Act, divided the District into three counties, Ohio, Monongalia, and Yohogania.

West Augusta District

The description of West Augusta District, in the Act, was as follows: "Beginning on the Allegheny mountain between the heads of Potowmack, Cheat, and Green Brier rivers, thence along the ridge of mountains which divides the waters of Cheat river from those of Green Brier, and that branch of the Monongahela river called Tyger's valley river to the Monongahela river, thence up the said river, and the west fork thereof, thence in a direct course to the head of Middle Island creek, a branch of the Ohio, and thence to the Ohio, including all the waters of the said creek in the aforesaid district of West Augusta, all that territory lying to the northward fo the aforesaid bounday, and to the westward of the states of Pennsylvania and Maryland, shall be deemed, and is herby declared, to be within the district of West Augusta."

Ohio, Monongalia, & Yohogania Counties

The description of the boundaries between the three counties, was as follows:
[Ohio] "Beginning at the mouth of Cross creek, thence up the same to the head thereof, thence south eastwardly to the nearest part of the ridge which divides the waters of the Ohio from those of Monongahela, thence along the said ridge to the line which divides the county of Augusta from the said district, thence with the said boundary to the Ohio, thence up the same to the beginning, shall be one distinct county, and be called and known by the name of Ohio county;"
[Yohogania] "and all that part of the said district lying to the northward of the following lines, viz. beginning at the mouth of Cross creek, and running up its several courses to the head thereof, thence south eastwardly to the nearest part of the aforesaid dividing ridge between the waters of the Monongahela and Ohio, thence along the said ridge to the head of Ten Mile creek, thence east to the road leading from Catfish camp to Redstone old fort, thence along the said road to the Monongahela river, thence crossing the river to the said fort, thence along Dunlap's old road to Braddock's road, adn with the same to the meridian of the head fountain of Potowmack, shall be one other distinct county, and be called and known by the name of Yohogania county;"
[Monongalia] and all that part of the said district lying to the northward of the county of Augusta, to the westward of the meridian of the head fountain of Potowmack, to the southward of the county of Yohogania, and to the eastward of the county of Ohio, shall be one other distinct county, and shall be called and known by the name of the county of Monongalia."

Extension of the western border of PA with VA to it's present line, removed all that part of Monongalia Co, north of the Mason Dixon line, as well as that part of Ohio, and Yohogania Counties east of the present PA/WV border. (80° 31' 8.2" W longitude) Yohogania was deemed to be too small to continue, and its territory was added to Ohio County.

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March 9, 2010