What you're looking at is the result of some very interesting research. A physicist named Dirk Brockmann was looking for sources of data to show mobility within the US.
[H]e stopped by the home of his old friend Dennis Derryberry in the green mountains of Vermont. Over a beer on the porch, he told Derryberry about his research. Derryberry asked: "Do you know about WheresGeorge.com?" You can think of WheresGeorge.com as a primitive FourSquare for $1 bills. "Georgers"--as users call themselves--"check in" their bills by entering the zip codes and serial numbers, then write or stamp "wheresgeorge.com" on the bill. If someone finds the bill and enters it again, they get a "hit."What he deduced from those data were a theory he calls "effective boundaries"--those natural regions defined by affinity, not lines on a map. The Northwest, you'll note, looks exactly like you'd expect it to. It captures Northern California, as Jefferson Staters always knew it should. That chunk of Malheur County where most of my family comes from in Eastern Oregon is properly aligned with Idaho--as I experienced the region in my youth. Northern Idaho--Sandpoint, Coeur d'Alene--are part of the Spokane region, not the Boise region. Behold the rest of the country:
Henry's ads?), which in turn thinks of Oregon roughly as often as it thinks of British Columbia. Colorado roughly stands alone--as it does in the beer world, too. California is part of a giant sunbelt. I'm surprised to see a bright line separating Wisconsin and Minnesota, but not at all surprised to see that New England is one unified Red Soxistan. That's exactly what it feels like there.
At the end of the day, it's all culture.