Although this route may appear to be a derivative of US 40, it does not follow any of the old US 40 alignment except for a portion of the Historic National Road in Fayette County from US 40 to Vandalia. IDOT has since truncated the eastern end of Route 140 to the town of Mulberry Grove with the intersection of US 40.
In 2007, IDOT decommissioned the portion of Route 140 from near the Bond and Fayette County line at Mulberry Grove, east to Vandalia. While that section of highway is no longer marked for Route 140, the state still maintains its Historic National Road signage.
In Bond County, the route passes through farmland and runs south of Old Ripley. Past Old Ripley, the highway meets Illinois Route 127; the two highways overlap until Route 127 turns south at the western edge of Greenville. Route 140 continues east through northern Greenville, passing Greenville Regional Hospital. After leaving Greenville, the route heads east until turning north at an intersection north of Smithboro. The highway then heads east-northeast toward Mulberry Grove, parallel to and north of U.S. Route 40. In Mulberry Grove, the route enters along Wall Street before turning north along Maple Street. The highway then turns east along Main Street before leaving the village and entering Fayette County.[5] The highway terminates east of Mulberry Grove at a junction with US 40.[4][6]
