Immediately after the effective date of this Code, the Department shall indicate the highways in each county highway system under the provisions of this Code on such effective date by marking them upon a map which shows the public roads and section lines in the county and shall file such map with the county clerk. The county clerk shall enter the map among his official records, and no changes in the county highway routes indicated thereon shall be made except when a change has been made in the county highway system in accordance with the provisions of Section 5--105 of this Code or when a county highway or part of it is vacated or relocated in accordance with Sections 5--109 or 5--110 of this Code.
605 ILCS 5/5-103