This old(er) post from Tropolism offers some great maps of the US in relation to agricultural production. Linked from radical cartography (a great site!), this work by Bill Rankin:

“Where does our food come from? (And where should we expect to find the “meat lobby”?) But notice the marked discontinuity in soybean production between the Dakotas and Minnesota or Iowa — different reporting methodology, or subsidies? And why is chicken production so clustered? Questions too sophisticated to be answered by these simple maps, alas.”

:: images via radical cartography