625 ILCS 5/11-304
Local authorities in their respective maintenance jurisdiction shall place and maintain such traffic-control devices, including temporary stop signs placed as a substitute for missing or damaged permanent stop signs required by the State Manual, upon highways under their maintenance jurisdiction as are required to indicate and carry out the provisions of this Chapter, and local traffic ordinances or to regulate, warn, or guide traffic. All such traffic control devices shall conform to the State Manual and Specifications and shall be justified by traffic warrants stated in the Manual. Temporary stop signs shall be placed in a manner to provide adequate visibility and legibility, and shall be placed within duration recommendations in the State Manual, unless circumstances require longer placement. Placement of traffic-control devices on township or road district roads also shall be subject to the written approval of the county engineer or superintendent of highways.
Local authorities in their respective maintenance jurisdictions shall have the authority to install signs, in conformance with the State Manual and specifications, alerting motorists of the tourist oriented businesses available on roads under local jurisdiction in rural areas as may be required to guide motorists to the businesses. The local authorities and road district highway commissioners shall also have the authority to sell or lease space on these signs to the owners or operators of the businesses.
625 ILCS 5/11-304