The classifications given by railroads to their steam locomotive fleets were as varied as the machines themselves with several different designations within a particular class! The Chicago and Illinois Midland steam locomotives were likewise characterized by a wide range of classes ranging from A to H. In any event, the information here is most certainly not a complete, all-time listing of C&IM's steam fleet and also is merely meant to list the general types of steam locomotives operated by the railroad.
The Chicago and Illinois Midland Railway was historically a Class I system but in later years after the American Association of Railroads (AAR) reclassified the railroad industry it became one of the many shortline systems found across the country. The C&IM was never a large railroad stretching a little over 100 miles in length at its largest. However, it did move vast amounts of coal in central Illinois to power plants located to the north. Interestingly, the C&IM did not gain its name from the fact that it reached Chicago but rather from the companies which owned the railroad. In 1996 the C&IM became part of the Genesee & Wyoming family of shortlines and its name was changed to the Illinois & Midland Railroad and today the I&M is a very successful operation.
While the C&IM was a rather small system it did roster some impressive steam locomotives including 2-10-2 Santa Fes and 2-8-2 Mikados (no doubt used in heavy coal drag service). Today, one C&IM steam locomotives is known to exist, a 2-8-2 Mikado preserved at the Museum of Transportation in St. Louis.
Class A-1
The C&IM's Class A-1 included its only roster of 4-4-0 Americans.
Class B-1
The C&IM's Class B-1 included its fleet of 2-8-0 Consolidations.
Class C-1
The C&IM's Class C-1 included more of its fleet of 2-8-0 Consolidations.
Class D-1
The C&IM's Class D-1 included more of its fleet of 2-8-0 Consolidations.
Class D-2, D-3, D-4
The C&IM's Class D-2, D-3, and D-4 included its fleet of 0-8-0 switchers.
Class E
The C&IM's Class E included its fleet of 2-8-2 Mikados ranging from Class E-1 to E-4.
Class F-1, F-2, F-3
The C&IM's Class F-1, F-2, and F-3 included more of its fleet of 2-8-0 Consolidations.
Class F-4, F-5
The C&IM's Class F-4 and F-5 included more of its fleet of 2-8-2 Mikados.
Class G
The C&IM's Class G included its fleet of 2-10-2 Santa Fes.
Class H
The C&IM's Class H included more of its fleet of 2-10-2 Santa Fes.
For more information on the steam locomotives like those operated by the Chicago & Illinois Midland consider Guide to North American Steam Locomotives by author George Drury, which includes nearly 500 pages of information on virtually all of the steam locomotive wheel arrangements and designs (including streamlined steamers) ever developed. The book is a great resource on steam locomotives and a fine reference tool; you should find it very useful.
Also, consider the book American Steam Locomotives from author Brian Solomon. While this publication does not include quite as much technical data as Guide to North American Steam Locomotives it is still a very good resource with lots of information and best of all, is loaded with photographs! If you're interested in perhaps purchasing these books please visit The Railroad Diamond by clicking the tab in the menu to your left marked "TRD Store".