Yohogania County, Virginia

Yohogania County was created by the new state of Virginia in 1776, in an area long disputed between Virginia and Pennsylvania. The county ceased to exist after the border dispute between the two states was resolved in the 1780s. Thus, it is sometimes referred to as a "lost county," although 1.5 million people live within the territory it once claimed, which encompasses two entire counties and parts of four others in two states.

The problem arose through the complex and conflicting manner of granting territory and defining boundaries during the Colonial period. The North American continent was not surveyed until long after various land grants were made to individual colonies, and such land grants and even governmental entities frequently overlapped.

Virginia's claim was for a wedge from their coastal area all the way to the Pacific Ocean. Pennsylvania's was for 5 degrees of longitude west of the Delaware River. By the 1770s it was obvious that the two claims overlapped, in the area that in 1773 had been designated by Pennsylvania as Westmoreland County, because settlers were moving into the area from both directions. Both claims included the entire southwestern corner of what is now Pennsylvania, west of the Laurel Ridge (Allegheny Mountains) and south of the Kiskiminetas, Allegheny and Ohio rivers. The major prize location was the confluence of the Allegheny and Monongahela rivers, forming the Ohio River, at the location of Fort Pitt, now the city of Pittsburgh. The disputes over which colony had authority over the area led to overlapping land grants to settlers and battles between Virginians and Pennsylvanians in the period 1774–1775. In 1774, a Virginian militia group even attacked and captured the Westmoreland County seat at Hannastown and arrested three Westmoreland County justices who refused to acknowledge the jurisdiction of Virginia.

Similar conflicts between Maryland and Pennsylvania had been resolved earlier, by 1767, through the work of two men chosen by Cecil Calvert, brother of Charles Calvert, 5th Baron Baltimore, proprietor of Maryland, and Thomas Penn and his brother Richard, sons of William Penn and proprietors of Pennsylvania. Astronomer Charles Mason, an acquaintance of Benjamin Franklin, and surveyor Jeremiah Dixon came from England to do this work. The line they located has since been known as the Mason–Dixon line or Mason and Dixon's Line. However, their authority extended west only as far as western Maryland, and did not resolve border conflicts between Virginia and Pennsylvania.

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