IC's Wisconsin Division - yes it did exist

Wisconsin division South Elmhurst to Freeport 94.80
Madison branch Freeport to Madison 61.59
Dodgeville branch Freeport to Dodgeville 65.32

Historical Sketch of the Illinois Central Railroad - Ackerman

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Illinois Central RR - The title of the Northern Division been changed to Amboy Division, that of the Middle Division to Pontiac Division, The Chicago Madison and Northern Railroad is now called the Wisconsin Division of the Illinois Central.

Official Railway Guide XXVIII

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The Illinois Central has changed the names of six of its operating divisions:

The name of the Chicago division has been changed to the Illinois division
The Peoria division to the Indiana division.
The Freeport division to the Wisconsin division.
The Dubuque division to the Minnesota division.
The Cherokee Omaha division to the Iowa division.
The Louisville division to the Kentucky division.
The railroad from Effingham to Indianapolis Ind heretofore known as the Indianapolis Southern will be operated as a part of the Illinois Central and will become a part of the Indiana division.

The "Conductor & Brakeman" Vol 28

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Preparation for New Locomotives Involves Extensive Terminal Improvements On the Illinois Central RR.  The acquisition of heavier locomotives on the Springfield Division between Centralia and Clinton, on the Wisconsin Division between Clinton and Freeport and on the Tennessee Division between Fulton and Paducah Ky, was preceded by the extension of passing tracks and yards enlargement of roundhouses installation of turntables and the rebuilding and strengthening of bridges. Notwithstanding the fact that the delivery of these locomotives was not to begin until some time in January 1921 the railroad company in May 1920 authorized the construction of the facilities to permit the operation of the first fifty engines

Railway Review - April 9, 1921   Vol 68