Chicago Subdivision (Chicago to Stuenkel) ST
Chicago Subdivision (Stuenkel to Champaign) ST
Gilman Subdivision (Gilman to Springfield) ST
Freeport Subdivision (Chicago to Freeport) ST
Dubuque Subdivision (Freeport to Dubuque) ST
Joliet Subdivision (Chicago to Joliet) ST
Heyworth Line (Clinton to Heyworth) ST
(formerly Clinton to Freeport)
Herscher Line (Otto to Herscher) S
Rantoul Line (Dewey to Rantoul) S
(formerly Le Roy to Potomac)
All lines were originally Illinois Central, except the Joliet Subdivision which was originally Alton Route and later Gulf Mobile & Ohio. That line and the Illinois Central Freeport Subdivision paralleled each other between 21st Street and Bridgeport. In 1996, the Joliet Subdivision was downgraded between those points, with all traffic diverted to the Freeport Subdivision.
South Bend Subdivision (Munster to Battle Creek) ST
In 2013, trackage west of Munster, formerly used to reach Chicago, was transferred to CSX.
Waukesha Subdivision (Chicago to Fond Du Lac) ST
Waukegan Subdivision (Waukegan to Leithton) ST
Leithton Subdivision (Leithton to Joliet) ST
Matteson Subdivision (Joliet to Gary) T
Illinois River Subdivision (Walker to Goose Lake)
Lakefront Subdivision (South Chicago to Gary) T
The 2009 acquisition of this line is resulting in changes in how the CN lines are connected. Improved connections have been constructed with the Waukesha Subdivision at Leithton, the Freeport Subdivision at Munger, the Chicago Subdivision at Matteson, and the South Bend Subdivision at Griffith.
Pontiac District (Saxony to Minonk) S
Aurora Line (Aurora to Normantown) S
Porter Line (Griffith to Porter) T
Short line companies which eventually acquired some trackage.
Former Illinois Central from Herscher to Bloomington