Edit: Moved TN info to its own post so the map could be prominent.
http://www.ilga.gov/legislation/ilc...SeqEnd=61700000&ActName=Illinois+Vehicle+Code.(625 ILCS 5/3‑413) (from Ch. 95 1/2, par. 3‑413)
Sec. 3‑413. Display of registration plates, registration stickers and drive‑away permits.
(a) Registration plates issued for a motor vehicle other than a motorcycle, trailer, semitrailer, truck‑tractor, apportioned bus, or apportioned truck shall be attached thereto, one in the front and one in the rear. The registration plate issued for a motorcycle, trailer or semitrailer required to be registered hereunder and any apportionment plate issued to a bus under the provisions of this Code shall be attached to the rear thereof. The registration plate issued for a truck‑tractor or an apportioned truck required to be registered hereunder shall be attached to the front thereof.
(b) Every registration plate shall at all times be securely fastened in a horizontal position to the vehicle for which it is issued so as to prevent the plate from swinging and at a height of not less than 5 inches from the ground, measuring from the bottom of such plate, in a place and position to be clearly visible and shall be maintained in a condition to be clearly legible, free from any materials that would obstruct the visibility of the plate, including, but not limited to, glass covers and plastic covers. Registration stickers issued as evidence of renewed annual registration shall be attached to registration plates as required by the Secretary of State, and be clearly visible at all times.