Illinois State Route 100 runs east-west in Western Madison County. This is the southern most county that it runs in. IL St Rt 100 passes through the following towns Madison County. Alton
Godfrey
Clifton Terrace
IL St Rt 100 is not multi-plexed in Madison County. IL St Rt 100 intersects the following highway in Madison County. U.S. Rt. 67, at Alton.
SB IL St Rt 100 at the Jersey/Madison County Line. A junction marker on NB U.S. Rt. 67. The southern start on NB IL St Rt 100. The southern end marker.
