The Chicago, Indianapolis & Louisville Railroad, known affectionately as the MONON, is Indiana's own. MONON derives from Potawatomi Indian words that sounded to the first settlers like metamonong or monong and seemingly meant "tote", or "swift running". In 1882, the railroad started printing "THE MONON ROUTE" on company maps, later naming itself "MONON - The Hoosier Line" on timetables, letterheads, and rolling stock.

Most Midwestern railroads built after the 1830's connected Eastern cities with the newly settled West. North-south lines stood as larger business risks. The MONON opened its 300-miles from Lake Michigan south to the Ohio River in 1853. As more railroads crossed Indiana, the MONON offered passengers and shippers links to the Southern at New Albany; the Baltimore & Ohio at Mitchell; the Milwaukee at Bedford; the Illinois Central at Bloomington; the Pennsylvania at Gosport; the New York Central at Greencastle; the Wabash and the Nickel Plate at Lafayette; the Nickel Plate at Linden; the Erie at Wilders, plus the Chicago & Eastern Illinois, the Chesapeake & Ohio, the Chicago, South Shore & South Bend, the Peoria & Eastern, the Grand Trunk Western, and the Louisville & Nashville at other points.

The few north-south railroads, such as the MONON and Illinois Central, provided timely service to Union forces during the Civil War. The MONON carried volunteers to mustering centers free; hurried sick, wounded or discharged men home at half-price. It carried troops, ammunition, food, fuel and medicine on contract. In 1861 alone, the government paid the MONON $9,149 to deliver 9,105 men to war-related destinations. Of 17 Indiana railroads running in 1861-65, only two carried more military personnel. A clue to the MONON's vital war role: Confederate John Morgan's raiders from Kentucky in July, 1863, tore out MONON tracks, pulled over water tanks, burned trestles and a depot at Salem, Indiana.

In April, 1865, a MONON engine pulled President Abraham Lincoln's funeral train at 5 mph, per orders, over the 90 miles from Lafayette to Michigan City, one of twenty railroad lines honored to participate in the 20-day, 1,666-mile trail of sadness from Washington, D.C., to Springfield, Illinois.

From 1854 on, the MONON provided inestimable service to the limestone industry of southern Indiana. Indiana limestone is unique because of its uniformity of color. A building constructed of Indiana limestone has the promise of identically colored limestone being available, should additional stone be necessary, even years later. Indiana stone was used to construct the Empire State building, the Pentagon, the National Cathedral, and countless private buildings, museums, bridges, churches, walkways, monuments, statues, and gravestones. Each new slab of Indiana limestone rode a MONON flatcar first, wherever its destination.

In 1946, John W. Barriger III became president of the MONON, changed its operations, built new passenger cars, purchased new diesel F-3's for passenger and mainline freight service, and made the MONON a modern, efficient, and competitive railroad. The MONON Railroad was the first class "A" railroad to become fully dieselized. It operated entirely within the state of Indiana, having only a few miles of out-state trackage rights to connect it to its two major terminals - Chicago and Louisville, Kentucky.

A map of the MONON trackage would show it in the form of an "X", laid out over the state of Indiana. One leg ran from Dearborn Station in Chicago, Illinois to Union Station in Indianapolis, Indiana, the first Union Station in the United States. The second leg ran from Michigan City, Indiana to Louisville, Kentucky. The "X" crosses at its namesake city of Monon, Indiana. The main line, runs from Chicago to Monon to Louisville, while the lines from Monon to Michigan City, and from Monon to Indianapolis, were operated as branch lines. Another branch line ran from Orleans, Indiana, Southwest, stopping at the West Baden Resort Hotel, and terminating on the grounds of the French Lick Springs Hotel, where it connects with the Southern Ry.

The MONON served five major Universities in Indiana, Purdue University (West Lafayette), Wabash College (Crawfordsville), DePauw University (Greencastle), Indiana University (Bloomington), and Butler University (Indianapolis). The state's decision to put Purdue University at Lafayette in 1869 had partly to do with MONON service, there since 1852. So important was the college traffic that the road painted its passenger rolling stock the red and gray of Indiana University, and painted its freight engines black and gold of Purdue University. In 1959, after the Indianapolis to Chicago trains were discontinued, it didn't make sense to continue with two color schemes, and to economize, the red and gray passenger scheme was slowly converted to black and gold.

The MONON merged into the Louisville & Nashville Railroad in 1971, and some of the former MONON right of way is still operated today by CSX Transportation.