Illinois Route 40 (IL 40) is a north–south route in central portion of the U.S. state of Illinois. It runs from Interstate 74 (I-74) in East Peoria north to IL 78 at Mt. Carroll, just south of U.S. Route 52 (US 52) and IL 64. In 1935, IL 40 got cut back to Mount Carroll in favor of IL 78. By 1938, Illinois Route 88 entirely acquired IL 40 north of Sterling. In 1987, Illinois Route 5, a four-lane freeway, was designated Interstate 88 east of I-80, leading to two identically-numbered routes intersecting each other at an interchange. By 1995, IDOT redesignated IL 88 as IL 40 to prevent confusion. Although the new number is also the number of a Federal Highway that passes through Illinois (U.S. Route 40), a great enough distance exists between them that the possibility of confusing one for the other is negligible.
Prior to 2003, the Illinois 40 exit on I-74 southeast of Peoria was called "Industrial Spur". As part of the Upgrade 74 Project, the exit was renamed by the Illinois Department of Transportation to Riverfront Drive.