^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:
Illinois 159 then crosses Illinois 140 in rural Madison County...
Approaching Edwardsville, Illinois 159 joins Illinois 143 eastward. IDOT District 8 sure loves their split-phase sections with 4-section heads:
In Edwardsville, Illinois 159 straightens out to head south, crossing Illinois 157, and Illinois 143 takes this opportunity to turn eastward onto Illinois 157:
Leaving Maryville and entering Collinsville, Illinois 159 has an interchange with the Interstate55/70concurrency. IDOT didn't feel like including directions on top.
Shortly after that, the expressway portion of Illinois 15 in Belleville connects to Illinois 159 via a diamond interchange (I only got a sign photo at the southern intersection with the interchange ramps. Photography in the rain is hard).
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...