| Source: AniMap Plus: County Boundary Historical
Atlas: with "SiteFinder," U.S. Place Name Database and U.S. Cemetery Database.
(On CD.) Gold Bug Software, Alamo, CA. |
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| 1750 |
Cumberland Co. is formed from Lancaster Co. and unincorporated territory;
encompasses the entire southwestern quarter of Pennsylvania |
| 1771 |
Bedford Co. is formed from the western two-thirds of Cumberland Co. |
| 1773 |
Westmoreland Co. is formed from western Bedford Co.; the state of Virginia
forms the "West Augusta District" from northwestern Augusta Co., but it
includes Westmoreland Co., PA |
| 1776 |
Virginia creates Yohogania, Monogalia, and Ohio Cos. in the West Augusta
District |
| 1779 |
Virginia verbally agrees to the change in her border, but nothing is
carried out |
| 1781 |
Washington Co. is formed from western Westmoreland Co., includes parts
of Yohogania, Monogalia, and Ohio Cos., VA; most of what would be the final
Washington Co. , PA, was in Yohogania Co., VA; most of what would become
Greene Co., PA, was in Monogalia and Ohio Cos., VA |
| 1784-5 |
Boundary between Pennsylvania and Virginia is surveyed |
| 1786 |
Virginia formally terminates its jurisdiction in SW Pennsylvania; Yohogania
Co. ceases to exist |
| 1788 |
Allegheny Co. is formed from part of northeastern Washington Co. |
| 1796 |
Greene Co. is formed from southern Washington Co. |
| 1800 |
Beaver Co. is formed from part of northwestern Washington Co. |
| 1802 |
Washington Co. gains from Greene Co.; Washington Co. is now in its
final form |
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