Brand mapping.
A lot of stores have spread out over the country like a plague of sameness, ensuring that I can get the same uninteresting selection here in California as I do when I go back to Pennsylvania for Christmas. (If I bought Christmas gifts, this would really be problematic.)
But there remain certain localized stores that build cult followings; for me, these include Steak ‘n Shake, Wawa, and the supermarket I’ve mapped here, Wegmans. Wegmans locations are shown in the lower map, creating a crescent stretching from Erie, PA through New York and New Jersey down into Washington, DC. And, sure enough, if you map tweets about Wegmans, they neatly establish this same shape, showing that Wegmans lovers are right where you’d expect them to be.