The Monon Railroad (reporting mark MON), also known as the Chicago, Indianapolis and Louisville Railway (reporting mark CIL) from 1897–1956, operated almost entirely within the state of Indiana. The Monon was merged into the Louisville and Nashville Railroad in 1971, and much of the former Monon right of way is operated today by CSX Transportation. In 1970 it operated 540 miles of road on 792 miles of track; that year it reported 1320 million ton-miles of revenue freight and zero passenger-miles. (It showed zero miles of double track-- the longest such Class I railroad in the country.)

The Monon served six colleges and universities along its line:

The university traffic was important enough to the Monon that the railroad used the schools' colors on its rolling stock. The red and white of Wabash College (and very similar to the colors of Indiana University) was used on the railroad's passenger equipment, and the black and gold used by both DePauw University and Purdue University adorned the railroad's diesel freight locomotives and later replaced the red and white on passenger equipment as well.