Illinois State Route 18 runs across the southern portions of Putnam County. IL St Rt 18 is does not pass through any towns in Putnam County. IL St Rt 18 is multi-plexed in Putnam County. Illinois State Route 26, near Henry.
IL St Rt 18 intersects the following highways in Putnam County. Illinois State Route 26, near Henry.
EB IL St Rt 18/NB IL St Rt 26 at the Marshall/Putnam County Line. A junction marker on EB IL St Rt 18/NB IL St Rt 26. WB IL St Rt 18 at north IL St Rt 26. WB IL St Rt 18 east of north IL St Rt 26. WB IL St Rt 18 near 1000E Road. WB IL St Rt 18 west of IL St Rt 89. WB IL St Rt 18 at IL St Rt 89. WB IL St Rt 18 west of IL St Rt 89. WB IL St Rt 18 west of the La Salle/Putnam County Line. WB IL St Rt 18 at the La Salle/Putnam County Line.
