765 ILCS 130/4

When any person wishes to inclose his land, located in any county having less than 1,000,000 population according to the last preceding federal census and not within the corporate limits of any municipality in such county, each owner of land adjoining his land shall build, or pay for the building of, a just proportion of the division fence between his land and that of the adjoining owner and each owner shall bear the same proportion of the costs of keeping that fence maintained and in good repair. The provisions of this Section shall not apply to fences on lands held by public bodies for roadway purposes.