Illinois Central historically had named districts for all lines. In 1999 Illinois Central became part of CN. And the CN term subdivision was adopted, using the same names as the former districts.
Chicago Subdivision (Chicago-Stuenkel)
Freeport Subdivision (Chicago-Broadview)
Lines Sold to Metra
Main Line
South Chicago Branch
Blue Island Branch
Chicago Subdivision (Stuenkel-Champaign)
Gilman Subdivision (Gilman-Springfield)
Champaign Subdivision (Champaign-Centralia)
Effingham Subdivision (Effingham-Newton)
Herscher (Bloomington) Line (Otto-Herscher-Kempton)
Rantoul Line (Le Roy-Dewey-Rantoul-West Lebanon)
Line Sold to Bloomer Line (Short Line Operator)
Bloomington District (Kempton-Colfax-Bloomington)
Line Sold to Indiana Rail Road (Short Line Operator)
Effingham District/Indianapolis District (Newton-Indianapolis)
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 (Amboy) Line (Clinton-Heyworth-Freeport)
Line Sold to Decatur Junction Railway (Short Line Operator)
Clinton District (Centralia-Assumption-Decatur-Clinton)
Abandoned Lines
Springfield District (Springfield-Glen Carbon)
via C&NW (Glen Carbon-Madison IL)
Mattoon District (Mattoon-Evansville)
Havana District (Champaign-Havana)
Decatur District (White Heath-Decatur)
Centralia Subdivision (Centralia-Cairo)
Bluford Subdivision (Edgewood-Metropolis Jct.)
St. Louis Subdivision (East 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 (Broadview-Freeport)
Dubuque Subdivision (Freeport-Dubuque)
Abandoned Lines
Madison District (Freeport-Madison)
Dodgeville District (Red Oak-Dodgeville)
Joliet Subdivision (Chicago-Joliet)
Sparta Subdivision (St. Louis-Baldwin-Percy-Cairo)