Lines are grouped into historic operating divisions. As passenger service declined during the 1950's, many divisions were consolidated.
Illinois Central historically identified its lines as districts, prior to adopting the CN term subdivision.
Chicago Subdivision (Chicago-Stuenkel)
Chicago Subdivision (Stuenkel-Champaign)
Champaign Subdivision (Champaign-Centralia)
Centralia Subdivision (Centralia-Cairo)
Gilman Subdivision (Gilman-Springfield)
Effingham Subdivision (Effingham-Newton)
Herscher Line (Otto-Herscher-Kempton)
Rantoul Line (Le Roy-Dewey-Rantoul-Potomac)
Lines Sold to Short Line Operators
(Some segments abandoned prior to sale)
Bloomington District (Kempton-Colfax-Bloomington)
(BLOOMER LINE)
Effingham District/Indianapolis District (Newton-Indianapolis)
(INDIANA RAIL ROAD/part)
Abandoned Lines
Pontiac District (Saxony-Minonk)
Earlier Abandoned Lines
Tracy Branch (Buckingham-Tracy)
Connected with Bloomington District (now Herscher Line) at Buckingham.
Peoria Subdivision (Peoria-Mattoon)
Heyworth Line (Clinton-Heyworth)
Lines Sold to Short Line Operators
(Some segments abandoned prior to sale)
Clinton District (Centralia-Assumption-Decatur-Clinton)
(DECATUR JUNCTION RAILWAY/part)
Abandoned Lines
Springfield District (Springfield-St. Louis)
Mattoon District (Mattoon-Evansville)
Amboy District (Heyworth-Freeport)
Havana District (Champaign-Havana)
Decatur District (White Heath-Decatur)
Bluford Subdivision (Edgewood-Metropolis Jct.)
St. Louis Subdivision (St. Louis-Du Quoin)
Eldorado Subdivision (Du Quoin-Eldorado)
Abandoned Lines
Texas Line/Murphysboro District (Pinckneyville-Carbondale/Mounds)
Carbondale District + Branches (Carbondale-Paducah)
Earlier Abandoned Lines
B&C Line (Belleville-Carondelet)
Industrial spur near St. Louis.
Freeport Subdivision (Chicago-Freeport)
Dubuque Subdivision (Freeport-Dubuque)
Abandoned Lines
Madison District (Freeport-Madison)
Joliet Subdivision (Chicago-Joliet)
Sparta Subdivision (St. Louis-Baldwin-Percy-Cairo)