NPR has a brilliant piece today by Robert Krulwich on mapping regional communities in the USA, both by tracing the limits to the circulation of dollar bills and patterns of telephone usage.
Dirk Brockmann, at Northwestern processed the data from the US Treasury about bill circulation:
New England is pretty coherent by both measures, but the rest of the country breaks down along lines that have little to do with state boundaries. I especially appreciate that the circulation of dollar bills suggests several boundaries of different strengths, giving some nuance in the classification.
The full essay is excellent ~ go read it!
h/t Lina Del Castillo