The Chicago, Indianapolis & Louisville Railway, otherwise known as the Monon, formed a gigantic X across the state of Indiana. Its earliest antecedent, New Albany & Salem, had projected a route between its namesake Indiana towns, the former being located on the Ohio River opposite Louisville. During the middle decades of the nineteenth century, this route evolved into the Louisville, New Albany & Chicago, which in 1883 merged with the Chicago & Indianapolis Air Line Railway. The two routes crossed at the village of Monon, Indiana, from which the railroad took its trade name. The merged railroad retained the name after it was reorganized in 1896 as the Chicago, Indianapolis & Louisville Railway.
Chronic financial problems dogged the line. It trimmed passenger operations to a minimum, but still the company struggled through the 1930s and was reorganized in 1946, with John W. Barriger III as president. Barriger’s administration modernized the railroad in postwar fashion with diesels replacing steam, among other improvements, including a trio of named passenger trains. In the mid-1960s, Monon ordered a small fleet of Alco C-628 diesels to handle an anticipated coal boom. Alco delivered the big six-motor diesels in handsome black and gold paint, but the traffic failed to materialize, so Monon traded them back for more versatile C-420 units. Monon served to forward traffic from Chicago to the Louisville & Nashville at Louisville, but was swept up in the 1960s merger-mania. On August 1, 1971, it was merged with L&N.