For Wisconsin, I can tell you Milwaukee Road/Soo Line/GB&W/FRV (FRV was all former CNW track by the way) or Wisconsin Central (depending on era), and WSOR (Wisconsin and Southern). Add to that the GBW agreement with BN (mostly intermodal) and you have a wider variety still. Then there's Soo Line being owned by CP, which adds a bunch of other possibilities (Canadian freight). So, it goes to prove that you can get away with running almost anything on any layout.
Side thought to prove my point further: I live in a city that never had much for rail service, and the last train was in either the late 60s or early 70s. A *very* small operation (entire fleet consisted of 2 switchers), and yet somehow we had a Santa Fe boxcar make it all the way up here (mind you, this was when it was still Santa Fe, and the furthest their track went was Chicago). To tell you how far it traveled, that means it would have started (at the very least) in Chicago, worked its way to Green Bay, and then connected at least once (possibly twice) after that still.