Where Are All the Prairie Potholes?

I've blogged before on the prairie potholes, most recently here.  EWG has a set of maps which outline the pothole region, as well as where grassland and wetland have been converted to active cropland recently.

Note my use of "active"--that's because by definition every acre in the Conservation Reserve Program once was cropped/considered by FSA/ASCS to be cropland.