65 ILCS 5/11-84-7
Except as herein otherwise provided for municipalities of more than 500,000 population, all contracts for the construction or repair of sidewalks as provided in this Division 84, when the expense thereof exceeds $1,500, shall be let to the lowest responsible bidder in the following manner: Notice shall be given by the officer or board designated in the ordinance to take charge of the construction or repair and supervision of a sidewalk, by advertisement at least twice, not more than 30 nor less than 15 days in advance of the day of opening the bids, that bids will be received for the construction or repair of that sidewalk in accordance with the ordinance therefor, in one or more newspapers published within the municipality, or if no newspaper is published therein, then in one or more newspapers with a general circulation within the municipality. In municipalities with less than 500 population in which no newspaper is published, publication may instead be made by posting a notice in 3 prominent places within the municipality. The notice shall state the time of opening the bids. All bids offered shall be accompanied by cash or a check payable to the order of the officer or board having charge of the improvement, and certified by a responsible bank, for an amount which shall not be less than 10% of the aggregate of the bid. All contracts shall be approved by the officer, or the presiding officer of the board, having the supervision of the construction or repair of that sidewalk.
In municipalities of more than 500,000 population, the letting of contracts for the construction or repair of sidewalks as provided in this Division 84 shall be governed by the provisions of Division 10 of Article 8.
65 ILCS 5/11-84-7