Rampant land speculation and vaguely worded colonial charters resulted in conflicting claims to the territory surrounding the Monongahela Valley in the late colonial period. Pennsylvania installed the Westmoreland County government at Hanna's Town, near present Greensburg, in April 1773. In response, Virginia's governor, Lord Dunmore, asserted Virginia's jurisdiction by establishing a military presence in western Augusta County, appointing John Connolly commander of militia at Fort Pitt, in present Pittsburgh. On December 12, 1774, Dunmore ordered the Augusta County government moved from Staunton to Fort Pitt, creating the District of West Augusta by proclamation.

When revolution against the British appeared inevitable, the Virginia Convention of July 1775 supported the American cause. An act of that convention established 16 military districts, including West Augusta, granting the district two delegates and one senator in the Virginia legislature and authorizing the continuation of the county government.

In 1776, the Continental Congress was petitioned to form a new state called Westsylvania from the territory comprising West Augusta. The petitioners' grievances concerned uncertain land titles, discord between Virginia and Pennsylvania, and ineffective local government exacerbated by West Augusta's great distance from the seats of state government. However, Pennsylvania and Virginia were hostile to the creation of Westsylvania, and the Continental Congress lacked the authority to create a new state.

On October 7, 1776, the Virginia General Assembly identified the boundary of West Augusta for the first time in the very legislation that abolished it and created three new counties, Monongalia, Ohio and Yohogania. Present southwestern Pennsylvania and northern West Virginia were within the boundaries defined. The District of West Augusta's representatives and court were transferred to Yohogania County. Virginia appointed a commission to settle conflicting land claims, but its biased decisions further antagonized the Pennsylvanians. In 1784, the completion of the Mason-Dixon line survey, slicing through the center of what had been West Augusta, established the boundary between Virginia and Pennsylvania and concluded their territorial dispute.