IL 35 begins at a four-way urban intersection in East Dubuque.

From here, IL 35 heads northeast out of East Dubuque on a curving route.

Once it leaves East Dubuque, IL 35 becomes a primarily rural road, which it remains for the rest of its route.

The highway passes County Route 5W shortly before becoming WIS 35 at the Wisconsin state line.

[5] By 1936, Illinois Route 37 entirely acquired IL 147 south of Marion.