Not just the Appalachians; any natural barrier between the coast/Piedmont and the place under test will work. But IMO, it's mostly about the settlement pattern

Not just the Appalachians; any natural barrier between the coast/Piedmont and the place under test will work. But IMO, it's mostly about the settlement pattern in play. I've found Colin Woodard's "American Nations" to be a pretty good guide. I think this map comes from that: http://static.businessinsider.com/image/55b273a2371d2211008b9793/image.jpg http://static.businessinsider.com/image/55b273a2371d2211008b...