Former Alton Route/Gulf Mobile & Ohio

Alton Route historically had numbered subdivisions, which were retained after the 1947 acquisition by Gulf Mobile & Ohio. The old Gulf Mobile & Ohio used named districts. In 1972, Gulf Mobile & Ohio merged with Illinois Central forming the Illinois Central Gulf Railroad. And Illinois Central's use of named districts was adopted. In 1987, these lines were sold to the newly formed Chicago Missouri & Western Railway. Which quickly went bankrupt, and in 1989 the lines were sold to Southern Pacific, which in 1996 became part of Union Pacific. Union Pacific continues to use named subdivisions.

via CN (Chicago-Joliet)
Joliet Subdivision (Joliet-Bloomington)
Pequot Subdivision (Pequot-Mazonia)
Springfield Subdivision (Bloomington-Alton)
Joint Line (Alton-East St. Louis)

Abandoned Lines

Washington Branch (Dwight-Washington)
P&N Branch (Peoria-Springfield)

Earlier Abandoned Lines

Barnett Branch (Carlinville-Barnett)
Connected with main line at Carlinville.

East Hardin Branch (Carlinville-East Hardin)
Connected with main line at Carlinville.