Illinois Route 70 is a state road in far north-central Illinois. It runs from Illinois Route 75 in Durand to Business U.S. Route 20 in Rockford. This is a distance of 19.01 miles (30.59 km).

Illinois 70 is the main route northwest of Rockford, and is called Kilburn Avenue and Trask Bridge Road in this area. The route serves mainly rural areas and consists of two-lane undivided surface street for its entire length.

SBI Route 70 ran from Durand to Rockford to Mendota, located about 60 miles (97 km) south of Rockford. In 1940, U.S. Route 51 replaced Illinois 70 from Mendota to Rockford, and Illinois 70 was pulled back to its current intersection with what was then U.S. 20.