The Chicago and Eastern Illinois Railroad was a Class I railroad that linked Chicago to southern Illinois, St. Louis, and Evansville. Founded in 1877, it grew aggressively and stayed relatively strong throughout the Great Depression and two World Wars before finally being purchased by the Missouri Pacific Railroad and the Louisville and Nashville Railroad (L&N). Missouri Pacific merged with the C&EI corporate entity in 1976, and was later acquired itself by the Union Pacific Railroad.

The Missouri Pacific Railroad, commonly abbreviated as MoPac, was one of the first railroads in the United States west of the Mississippi River. MoPac was a Class I railroad growing from dozens of predecessors and mergers. In 1967, the railroad operated 9,041 miles of road and 13,318 miles of track, not including DK&S, NO&LC, T&P, and its subsidiaries C&EI and Missouri-Illinois.