I grew up in a part of Appalachia where half the population had a noticeably heavy accent, and the other half of the population had a more traditional standard

I grew up in a part of Appalachia where half the population had a noticeably heavy accent, and the other half of the population had a more traditional standard American accent (broadcast English or general American, there are various names for it). The separation was often elaborated as creek vs crick people, based on how they pronounced the word creek. Interestingly the speech patterns were not solely an economic division (maybe 2/3 of the division was along an economic line), you would have one working poor family with the country/rural accent, and another working poor family next door that would have a standard American accent instead. It was always interesting to trace the roots of that based on where the families originated from (typically PA, MD, WV, VA, OH in the part of Appalachia I was from; as opposed to southern Appalachia), as it was pretty much always a family based accent distribution; the family history largely dictated the creek vs crick language division.