^Northbound trailblazer at Illinois 158 in Belleville, February 2023.
Illinois Route 159 is a north-south highway in the Metro-East that extends into adjoining areas to the north and to the south. Its northern end is at Illinois 16 west of Gillespie, and the southern end is at Illinois 3 and Illinois 154 at Red Bud, Illinois.
From north to south, Illinois 159 gets its start at Illinois 16 west of Gillespie:
North of Hecker, Illinois 156 comes from the east to join Illinois 159 south:
Shortly after that, in Hecker, Illinois 156 deviates to continue westward:
Illinois 159 reaches its southern end at a 4-way intersection in Red Bud, where Illinois 3 comes from the west and turns southerly, and where Illinois 154 begins to head east...