Coal traffic
Bituminous coal represented the largest volume item for the C&EI, constituting about one-third of all C&EI traffic. Coal was the primary traffic in the Westville, Salem and Mt. Vernon areas of Illinois and the Clinton and Terre Haute areas of Indiana. A major portion of the coal generated by mines on the C&EI was destined for Chicago or the barge loading facility at Joppa, Illinois. So much coal was destined for the Chicago region steel mills that, for many years, the Elgin Joliet and Eastern (EJ&E) paid the C&EI for trackage rights to move their trains over the C&EI between its company-owned rails in the Chicago area and the coal mines located at Sidell and Westville on the C&EI.

Bridge traffic
Because C&EI rails connected with the rails of many other railroad companies, the C&EI moved a large volume of traffic that was neither generated on, nor destined for industries served by the C&EI. Rather, the C&EI acted as a bridge between these many connections with cars moving between railroads over the C&EI. Thus, for example, the C&EI might help move automobiles produced in Detroit to dealers located beyond Illinois, an series of interchanges that might involve several railroads.

This bridge traffic was a major source of revenue for the C&EI. More than half of all freight was for interchange, primarily the Louisville and Nashville in Evansville, the Missouri Pacific and western carriers in St. Louis, the Wabash in Danville and numerous carriers in the Chicago area through the Belt Yard and other connections. The IC, NYC, NKP, and PRR were major connections away from the larger cities.