Possibly, but most US produce comes from low-density areas. By definition, otherwise nobody could afford massive acreage. That means the less populous parts of

Possibly, but most US produce comes from low-density areas. By definition, otherwise nobody could afford massive acreage. That means the less populous parts of California, Arizona, and Florida. It'd be interesting to do an upstream drainage trace though, as many rivers do flow through urban areas. Although less so in California? Given they're mostly mountains-to-sea, so would hit fields before major coastal population centers?