, looking west First constructed in 1971, I-72 ran from
Springfield at
I-55 to
Champaign at
I-57 until the 1990s. On June 9, 1991, the
American Association of State Highway and Transportation Officials (AASHTO) approved the establishment of
I-172 from the western terminus of I-72 at Springfield to
Fall Creek, east of
Hannibal, Missouri, though it was contingent on
Federal Highway Administration (FHWA) approval. The FHWA preferred to designate the route I-72. After discussions regarding extending an Interstate Highway through the state of Missouri, on April 22, 1995, AASHTO approved another renumbering. I-172 was renumbered in its entirety as I-72. The
US 36 extension west of Fall Creek was also given the I-72 designation. The
Illinois Route 336 (IL 336) expressway was renumbered to I-172 from Fall Creek to
Fowler. , near
Valley City,
Illinois. Prior to September 2000, Mark Twain Avenue (old US 36) was composed of the current Mark Twain Avenue (now
Route 79) and the portion of I-72 and US 36 west of exit 157 to the Hannibal city limits. Route 79 terminated at the foot of the old
Mark Twain Memorial Bridge at the corner of Third Street and Mark Twain Avenue. Signs along the four-lane expressway portion of Mark Twain Avenue marked the route as "Future I-72", while signs along what is now Route 79 had I-72 trailblazers to direct drivers to the temporary terminus at Fall Creek, Illinois. When the new Mark Twain Memorial Bridge was completed in September 2000, I-72 was routed over the new bridge, along with US 36. Route 79 was extended along Mark Twain Avenue to terminate at exit 157.
Chicago–Kansas City Expressway The concept of I-72 across
Missouri was to create the
Chicago–Kansas City Expressway, a rural four-lane highway across northern Missouri and west central
Illinois from
Cameron, Missouri, at
I-35 to
Springfield, Illinois, at
I-55. This would provide a series of rural four-lane highways (I-35, US 36, I-72, and I-55) connecting Chicago to the
North American Free Trade Agreement (NAFTA) Corridor (
High Priority Corridor 23). This would reduce the amount of through traffic, primarily truck traffic, in the
St. Louis,
Des Moines, and
Quad Cities metropolitan areas by serving as an alternate route for
I-70 and
I-80. The Missouri portion of this route is designated as part of
High Priority Corridor 61. Based on the marker at Route 79, if/when
US 36 is upgraded to
Interstate standards across Missouri, the future western terminus of I-72 would be at Cameron at the intersection with I-35. Currently, the west end of I-72 route is west of
US 61 and flows concurrent with US 36 into Illinois. In 2004, US 36 was upgraded to a four-lane expressway between US 61 and
US 24 at the Rocket Junction (). There are three exits along this expressway: Veterans Road, Shinn Lane (Hannibal Regional Hospital), and US 24 east at the Rocket Junction. Also, an interchange with
Route 15 was installed in
Shelbina. Due to funding priorities, upgrading US 36 between
Macon and
Hannibal was a low-priority project and was shelved. The
Missouri Department of Transportation (MoDOT) committed to constructing the four-lane highway as an at-grade expressway only if the five counties served by US 36 east of Macon would contribute half of the $100 million (equivalent to $ in ) cost. Road construction to complete the between Hannibal and Macon began in 2007. In August 2010, the four-lane expressway was completed from Macon to Hannibal, completing Missouri's portion of the Chicago–Kansas City Expressway. == Future ==