Illinois State Route 100 runs breifly in Western Morgan County. Most of this highway runs along U.S. Rt. 67. It runs along the eastern bluffs of the Illinois River Valley. IL St Rt 100 does not pass through any towns in Morgan County. IL St Rt 100 is multi-plexed in Morgan County. U.S. Rt. 67, from the Cass/Morgan County Line to near Meredosia.