There's a report out from Alter, Fuller, Sontheimer and Seigworth at Penn State, with good summary coverage by Jeff McGaw at the Reading Eagle. It shows how there are really two Pennsylvanias, economically speaking. While this isn't surprising, the degree and timing of the divergence is.
Besides being my home state, Pennsylvania might interest you because it's a swing state, which is in turn directly related to the mix of cultures and economies that comprise it. Pennsylvania is part Northeast/Mid-Atlantic, part inner Midwest/Rustbelt, and - often ignored, but quite important in these numbers - part Appalachia. Overall the state is lagging all of its Northeastern neighbors except for one (more on that in a second), because Pennsylvania's numbers are an average of two regions - the sucessful region (Philly and southeastern PA, which have done quite well after the 2008 recession) and then the rest of the state.
You can see the figures at the report and article, but here are two instructive maps. The top is the county-level 2016 presidential election data. On the bottom is (from Alter et al's article) county resident employment in the post-recession period 2008-2016. Even if you don't know PA geography, the resemblance is obvious.
It turns out the only state that Pennsylvania beats in the Northeast group is West Virginia. That's not a coincidence. The central-and-western PA counties have numbers that look remarkably similar to West Virginia's post-recession numbers in terms of jobs lost and unemployment, but when averaged with Philly and suburbs, these quite-bad numbers are obscured and you end up with one mediocre-looking state, instead of a very depressed large rural region, and a very successful metropolitan area. West Virginia comes across as struggling much more clearly, because it's the only state entirely within the Appalachians. (The Bad Stripe, a demographic region of bad quality-of-life and human development indicators, roughly corresponds to "Greater Appalachia" and does extend a bit into Pennsylvania.)
So these maps tell two stories. First, it's a cliche of campaign strategists and the cultural commentariat that Pennsylvania is "Philly on one end, Pittsburgh on the other, and Alabama in between." But that's not exactly right. Pennsylvania is Appalachia, with Philly and suburbs in one corner. And remember all those angry unemployed coal miners we've heard so much about? They live in Appalachia. Second, the late 90s/early aughts began the renaissance of the Northeastern American city, and even the recession couldn't stop that positive momentum. The divergence you see in these numbers and maps of Pennsylvania is both these stories, playing out in the same state and hidden by being averaged together.
The problem is that coal has been dead in PA for decades, and many of the people demanding its return at this point have never even worked in the industry - more likely, their fathers did, and that's what they view as important valuable work. It's a cultural problem. We all know that coal is not coming back and that it has everything to do with changing technology and nothing to do with regulations, a narrative that people in this part of the country have a hard time accepting. (Abstract economic forces are much harder to viscerally hate than bad people hurting you by design.) What's worse, the big cities like Philly, filled with untrustworthy people unlike you, have come roaring back; worse still, this happened just as media became all-pervasive and started constantly reminding you that these people look down their nose at you. Att least before, you might have been unemployed and living in Clearfield County, without being constantly reminded you were on the bottom of a status hierarchy that was exactly inverted, with the most immoral people at the top.
The reality is, for all us blue-staters in the suburbs and cities, these numbers show you that even though your suburb might be getting better all the time, things really are bad out there in the hinterlands, and this is why they were so desperate for a change they voted for Trump. And they're going to vote for Trump again as long as we don't show some solidarity with our countrymen and ignore their problems or even dismiss them with active contempt, which I admit I've been tempted to do myself. It may be taking a while for people to accept that coal is dead, but it's certainly not their fault. I don't have a clear policy prescription for how to help life get better in interior Pennsylvania, but taking people's problems seriously seems like a good place to start - which I deeply hope the Democrats can do in 2018 and 2020, or Trump will get re-elected.
 Many people called the 2008 recession a "man-cession", with men disproportionately hit relative to women. Nowhere was this more likely to be true than Pennsylvania, with effects lingering until today. Construction and construction-adjacent industries were propped up by capital flowing in from the cities, and now that those easy loans have dried up, construction isn't coming back either. This region is part of the "health belt", because it has an overabundance of older people, and the one source of capital coming into this region that has grown is Federal dollars in the form of Medicare disbursements. Therefore, many of the un- and under-employed men in the regions lost their construction-related jobs, and have wives working in nursing or other healthcare fields who became the breadwinners, a final slap in the face for many men in the region.
 More than once, both online and in person, I've seen urban and suburban centrists or liberals express sympathy for the plight of people in another country whose luck went south when the local mineral deposit was played out, then in the same conversation, say about fellow Americans essentially, "Coal is dead, get over it losers." If Democrats want to win elections at some point, this attitude has to stop, because human beings are good at detecting contempt - especially ones going through tough times - and they don't react well to it.
 Mountainous regions tend to be poorer than non-mountainous regions because it's hard to grow crops there - and the difficulty of agriculture means little opportunity for a service economy to develop on top of a farming and trading population. There are exceptions to the rule (e.g. Jackson, WY) but those are based on outside capital brought in by wealthy in-migrants or tourists in recent times. Out of curiosity I looked at Colorado to see if a similar relationship exists between election returns, economics and mountains, as in PA (the eastern half of CO is flat prairie and the western half is the Rockies.) Eyeballing it, there may be some pattern, but certainly not as clear as for PA. Speculatively, it could be that PA's mountains are smaller, and have been settled for (generations) longer, therefore producing an actual population that shows the impact of "bad mountain economies" - as opposed to CO, which has a much more thinly scattered population and may be more mobile relative to what resources there are. Concretely: a coal mine opens in the PA Appalachians in 1850 and a town grows up around it, which doesn't just evaporate when the mine is played out by 1970 - by this point the families have been there for generations, and the climate isn't so harsh, and leaving just isn't really considered. (Although counter to my theory, there are ghost towns in PA.) Versus CO, where an unobtainium mine opened in 1950, and today is just about played out - but the settlement around it is a high-turnover one of mostly youngish men who aren't living at 10,000 feet elevation for fun, and they clear out (or a few remain and develop the area for tourism, e.g. Leadville.)