605 ILCS 5/5-503
Bridges, culverts or drainage structures for across highway waterways having a waterway opening of 25 square feet or more and located on county highways, township roads or district roads on county lines, and bridges, culverts or drainage structures for across highway waterways having a waterway opening of 25 square feet or more and located on such county line highways where such highways deviate from the established county line within 80 rods of county lines, shall be constructed and repaired by such counties and the expense of such construction and repair shall be borne in a proportion to the assessed value of the taxable property in the respective counties according to the last preceding equalized assessment thereof prior to such construction or repair. The county boards of such adjoining counties may enter into joint contracts for a division of such expense other than that above provided which may be just and equitable, and such contracts may be judicially enforced against such county boards, and such county boards may be proceeded against jointly, by any parties interested in such bridges, culverts or drainage structures for any neglect of duty in reference to such bridges, culverts or drainage structures for any damages growing out of such neglect.
When any county desires to construct or repair any such bridge, culvert or drainage structure and has appropriated its share of the cost of constructing or repairing the same, it shall be the duty of such other county to make an appropriation for its proportionate share of the expense of such construction or repair. If such other county fails or refuses to make such appropriation, any court of competent jurisdiction, upon a petition for that purpose, shall enter an order to compel such other county to make such appropriation; or the county which has made its appropriation may, after giving due notice to the other county, proceed with the construction or repair of the bridge, culvert or drainage structure and if the construction or repair is reasonable in kind and costs, recover from the other county, by suit, such proportionate share of the expense as the other county is liable for, with costs of the action and interest from the time of the completion of the construction or repair, but, if the expense of the construction or repair of the bridge, culvert or drainage structure is unreasonable then the county may recover only the other county's proportionate share of an amount equal to a reasonable expense for the construction or repair.
605 ILCS 5/5-503