Interstate 72

I-72 runs for just over two miles (3.2 km) in the state of Missouri. Its western terminus is an interchange with US 61 to the Mark Twain Memorial Bridge over the Mississippi River. This bridge connects the city of Hannibal with Illinois. Presently, there are only two exits for I-72 in Missouri.

I-72 parallels the old Wabash Railroad from Hannibal, east through Illinois to Champaign, Illinois. The Norfolk Southern Railway operates this railroad route today.

In Illinois, I-72 runs for 182 miles (293 km). The portion of I-72 and I-172 from Springfield to Quincy is commonly referred to as the Central Illinois Expressway (CIE). As of 2007, I-72 has one business route; I-72 Business (I-72 Bus.) in Jacksonville.

Near Valley City at mile-marker 42 are the Valley City Eagle Bridges. These two individual two-lane spans bridge the Illinois River in rural west-central Illinois. Near milemarker 78, a sign marks 90 degrees longitude.

At its eastern terminus in Champaign, I-72 continues as Church Street (westbound) and University Avenue (eastbound), which stay as one-way streets for an additional three miles (4.8 km) into downtown Champaign.

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 157-mile (253 km) 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 (seven miles (11 km)). 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 $123 million in 2021[5]) cost. Road construction to complete the 52.4 miles (84.3 km) 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.[6]

I-72 currently has one auxiliary route, I-172, that serves as a freeway spur for Quincy.

Interstate 72 Business (I-72) is a business loop of I-72 in Jacksonville. It runs from the I-72/US 36/US 67 interchange southwest of Jacksonville north along the US 67 bypass of Jacksonville to the former alignment of US 36 (Morton Avenue). On Morton Avenue, I-72 Bus. runs east through downtown Jacksonville until it reaches I-72 at exit 68. This is a distance of 9.5 miles (15.3 km).[13]