I saw the following mammal. I thought it was a fox but not one I'm am familar with. It had a long slender body, slender face , and a banded tail (black and brown). The tail was all most as long as the body and it was full. The tail was carried straight bach in line with the body. The head looked mostly black and the body tending from black at the top of the back to brown at the lower body.

Sounds like a raccoon. Juveniles can look rather slender. That's the only species in IL with a black and brown banded tail.