Well, SC, I'm giving you the Illinois definition of rugged, which might be considered laughable in places like West Virginia. Pennsylvania, etc., Seriously, there probably is a dropoff in conductivity in far northwest Illinois or in the "Illinois Ozarks" south of Marion. But I've never noticed much effect anedotally driving through either area.
I've been all over Iowa. First as a college kid in Southeast Iowa, then with a girl I was dating for a couple of years in the northwest part of the state, then later still with customers in Des Moines, Cedar Rapids, Fort Dodge, and Davenport. And finally with both a son and a daughter who are graduates from the University of Iowa in Iowa City. I've never been to Eldon, however, although I have been to Anamosa and a few other nearby towns. I'm also familiar with Carl Smith by reputation, but I wasn't aware of his connection with the American Gothic house. Very cool!