Southwest Pennsylvania


This region encompasses 12 counties: Allegheny, Armstrong, Beaver, Butler, Cambria, Fayette, Greene, Indiana, Lawrence, Somerset, Washington, and Westmoreland.


Southwest Pennsylvania Region Map


In 1773, Westmoreland County was established, the first in Pennsylvania west of the Allegheny Mountains. All or parts of several other southwestern counties were formed from it: Washington (1781), Fayette (1783), Allegheny (1788), Greene (1796). In 1795, Somerset County was formed, followed in 1800 by Armstrong, Beaver, and Butler counties; then Cambria and Indiana in 1803, and finally, Lawrence in 1849. This development reflects the population growth west of the Alleghenies between 1790 (75,000) and 1800 (139,000).





The first European settlers to this area were primarily English and came from Maryland and Virginia on Braddock’s Road in the 1760s. In fact, as of 1754, Virginia had claimed some of the region as its own, offering land warrants called “Virginia Certificates.” In Map of Braddock's Military Road1784-85, the dispute was settled, and the present-day boundaries of Pennsylvania were drawn, establishing ownership of what became Westmoreland, Fayette, Green, Washington, and portions of Allegheny and Beaver counties. As part of the agreement, Virginia Certificates were honored, so information about land claims in the area prior to 1780 typically is found among both states’ records.



The region also saw significant Scotch-Irish immigration after 1769, when Land Offices formed for sales of lands purchased from the Indians. The Scotch-Irish came from the eastern counties as well as from Maryland, and in the early 1770s, the lands west of the Monongahela River were settled; early Catholic families from County Donegal, Ireland, settled in Armstrong and northern Butler County. After the Revolution, the majority of settlers in southwestern Pennsylvania were Scotch-Irish, mingled with some English, Germans, and others.



Coal was a substantial factor in Pennsylvania’s industrial growth. By 1800, coal was a major industry in Pittsburgh, which owes its growth as a manufacturing center to its strategic location in the middle of bituminous coalfields where the Allegheny and Monongahela rivers converge to form the Ohio River, which flows almost 1,000 miles to the Mississippi River. The largest city in this Pittsburgh, Allegheny and Birmingham - ca. 1871region (and the second largest in the state, after Philadelphia), Pittsburgh became known for its steel industry in the 1900s – Pittsburgh gravity incline coal train, c 1907during World War II, it produced 95 million tons – but its mills are gone today, and the city is now best known for education, financial services, healthcare, robotics, and technology. The city's immigrant history is reflected in its German, Italian, Polish, African-American, and Jewish neighborhoods.




1803 Map of Western Pennsylvania Rivers



Geographically, this region lies west of the Appalachian Divide – the Appalachian Plateau stretches across the western and northern sections of Pennsylvania and covers more than half the area of the state. Fayette, Cambria, Somerset, and Westmoreland counties are part of the Laurel Highlands, an area around Laurel Hill and Chestnut Ridge of the Allegheny Mountains, southeast of Pittsburgh. The mountains in this region are the highest in Pennsylvania.





The Western Pennsylvania Genealogical Society (WPGS) provides genealogical information and support to the counties in this region.





GSP welcomes your suggestions, knowledge and guidance to genealogical resources within any area of Pennsylvania in which you live and do your own research. If you have information to share about local societies or repository resources, historical knowledge of the local area, or any other relevant genealogical information that could help people find their ancestors, please contact GSP so we can add this information to the County page.Thank You!




(Thank you to Jane Benner for her contribution to this page!)

Image credits:

Southwest Pennsylvania Region Map courtesy of

Top left: Map of Braddock's Military Road from Cumberland to present day Braddock, PA. 1755; Wikimedia Commons

Center left: Pittsburgh, Allegheny & Birmingham, drawn from nature, lithograph, Otto Krebs, c 1871. Courtesy Library of Congress, ID - LC-DIG-ppmsca-09260.

Center right: Coal train on a gravity incline near Pittsburgh, ca 1907. Courtesy Library of Congress, ID -LC-USZ62-96860

Bottom left: 1803 Map of Western Pennsylvania Rivers, Wikimedia Commons.