1764 blockhouse from Fort Pitt still stands here and is one of the oldest buildings in the region. Other notable rivers are the Youghiogheny River, flowing north from West Virginia and western Maryland to join the Monongahela just upriver of Pittsburgh, and which was the early route of penetration into Western Pennsylvania, the Kiskiminetas River, French Creek, a major passageway between Lake Erie and the Allegheny River for the Indians and early French explorers and traders, and the small Oil Creek in Crawford and Venango counties, where slicks gave an indication of petroleum reserves and in whose watershed the first oil well in the United States was drilled. The highest point in Pennsylvania, Mount Davis, reaches , and is located near the southern border of the state in Somerset County, approximately east of the southwestern corner, where the Appalachian Mountains enter Pennsylvania from the south. To the west and north of this point lies the Allegheny Plateau, a dissected plateau so eroded that it appears to be an interminable series of high hills and steep valleys. The peaks in the area are among the lowest in the East Coast highlands, but what they lack in height they make up in wide extent of land covered, which forms a vast formidable barrier for mile upon mile to overland travel from the coast. Northwestern Pennsylvania The city of Erie is the business center and cultural hub of Northwestern Pennsylvania. The compiled population of the region was estimated to be 938,516 in 2015. Although the only county with population growth was Butler, the deficit for all other counties was within 3%. The region also includes the Erie-Meadville, PA Combined Statistical Area. Northwestern Pennsylvania is home to the Allegheny National Forest, and is the heart of Pennsylvania's oil and gas economy. Education Western Pennsylvania is home to more than two dozen institutions of higher learning, including those listed below. (Seminaries are not listed) Allegheny College The Art Institute of Pittsburgh Community College of Allegheny County (several campuses) Community College of Beaver County Butler County Community College (several campuses) California University of Pennsylvania Carlow University Carnegie Mellon University Chatham University Clarion University of Pennsylvania Duquesne University Edinboro University of Pennsylvania Gannon University Geneva College Grove City College Indiana University of Pennsylvania (several branch campuses) LaRoche College Lake Erie College of Osteopathic Medicine Mercyhurst University Mount Aloysius College Penn Highlands Community College Pennsylvania State University (several