High Quality Content by WIKIPEDIA articles! Illinois Route 171 (IL 171) is a north–south state road in northeastern Illinois. It runs from U.S. Route 6 (US 6) in Joliet north to IL 72 at the Chicago–Park Ridge border. This is a distance of 38.61 miles (62.14 km). The section of IL 171 on Archer Avenue from Joliet to Summit is historically significant, originating as a Native American trail, and later serving for a time as part of the first numbered highway between St. Louis and Chicago.