A colleague in another department mentioned a “Where’s George” map which shows regions where dollar bills tend to circulate together. That is the blue lines on the U.S. map indicate places where bills tend NOT to cross.
Not surprisingly, not all currency boundaries correspond with state boundaries. There’s a fairly large boundary running through the center of Pennsylvania and another through the western part of Wisconsin.
From a linguistic perspective though it appears that some currency boundaries correspond to certain dialect boundaries. For instance, the PA line is almost exactly where the “pop” vs. “soda” line is in PA. Looking at the Pop vs Soda map, you can also see that there are multiple places where the currency line matches a dialect line (e.g. N. California/Nevada/Arizona lines, the Ohio river valley stood out).
When you think about it, there is some logic because both currency and dialectal forms are something shared within communities (specifically community networks). But I was amazed that there was as much overlap as there was.