55 ILCS 5/5-1067

Names of streets and highways; numbers of buildings and lots. A county board may name or may change the name of any street, lane, road or highway and may regulate the numbering of buildings and lots adjacent to any street, lane, road or highway in the unincorporated area of the county.

In counties under 1,000,000 population, a county board may name or change the name of any road in the county highway system or any trail under its jurisdiction.