Pittsburgh was founded a generation before the American revolution. Sure, there were parts of the state that would not be founded for another 100 years because of the mountains. The railroads and a hunger for coal and steel mostly fixed that.

Also, I’d not quite say that it’s State College, Pittsburgh, Erie and nothin. It’s not as well settled as what is around Philly for sure. But millions of people live in the went side of the state, even if their coal and steel hubs took a hit in the past couple generations.