Long recognized as a powerhouse of American industry, Western Pennsylvania is a large geophysical and socio-economic entity. It encompasses that portion of the state to the west of the Appalachian divide and included within the Mississippi drainage system of rivers.

The largest rivers in this area are the Allegheny River, which flows southward from the New York border, and the Monongahela River, which flows northward from West Virginia. These two rivers meet at the city center of Pittsburgh and join to form the Ohio River, which from that point flows an additional 981 miles southwest to the Mississippi River. The juncture of the Allegheny and Monongahela was historically regarded as strategic and the gateway to the interior of the continent from the east. At various times this junture has been called the Forks of the Ohio, Fort Duquesne, Fort Pitt, the Golden Triangle, and today, at its apex, Point State Park.