Illinois State Route 78 is a north-south highway in Central Carroll County. It runs the Carroll/Whiteside County Line, near Fair Haven, to the Carroll/Jo Daviess County Line, near Pleasant Valley. IL St Rt 78 passes through the following towns in Carroll County. Ideal Mt. Carroll
IL St Rt 78 is not multi-plexed in Carroll County. IL St Rt 78 intersects the following highways in Carroll County. Illinois State Route 40, at Mt. Carroll.
SB IL St Rt 78 south of Argo Fay Road. A junction marker on WB U.S. Rt. 52/IL St Rt 64. NB IL St Rt 78 at U.S. Rt. 52/IL St Rt 64. SB IL St Rt 78 south of U.S. Rt. 52/IL St Rt 64. NB IL St Rt 78 north of Seminary St. in Mt Carroll. NB IL St Rt 78 at Turnbaugh St in Mt. Carroll. NB IL St Rt 78 at Market St in Mt. Carroll.
