225 ILCS 440/3.12
"Business area" means any part of an area adjacent to and within 660 feet of the right-of-way which is zoned for business, commercial or industrial activities under the authority of any law of this State; or not so zoned, but which constitutes an unzoned commercial or industrial area as defined in Section 3.11. However, as to signs along Interstate highways, the term "business area" includes only areas which are within incorporated limits of any city, village, or incorporated town, as such limits existed on September 21, 1959, and which are zoned for industrial or commercial use, or both, or to portions of Interstate highways which traverse other areas where the land use, as of September 21, l959, was established by State law as industrial or commercial, or both.
With respect to signs owned or leased by the State or a political subdivision, an area zoned for business, commercial, or industrial activities that is adjacent to and within 660 feet of an Interstate highway and that is in Township 41 North, Range 10 East of the Third Principal Meridian, shall be deemed a "business area" for purposes of this Act. This zoning must have been a part of comprehensive zoning and not have been created primarily to permit outdoor advertising structures as described in 23 CFR 750.
225 ILCS 440/3.12