U.S. Federal Route 20 runs east-west in Southwestern Mc Henry County. It runs from the Mc Henry/Boone County Line, south of Garden Prairie, to the Mc Henry/Kane County Line, near Harmony. U.S. Rt. 20 passes through the following town in Mc Henry County. Marengo Harmony
U.S. Rt. 20 is not multi-plexed in Mc Henry County. U.S. Rt. 20 intersects the following highway in Mc Henry County. Illinois State Route 23, at Marengo.
WB U.S. Rt. 20 at IL St Rt 23. EB U.S. Rt. 20 east of Marengo Road.
