Chicago & North Western had numbered subdivisions until the late 1950's, then named districts briefly, and since the 1960's had named subdivisions.
Chicago Passenger Terminal (old)
Chicago Passenger Terminal (new)
Geneva Subdivision (Chicago-Elburn)
Geneva Subdivision (Elburn-Clinton)
Belvidere Subdivision (West Chicago-Rockford-Freeport)
Peoria Subdivision (Nelson-Peoria/I&M Jct.)
St. Louis Subdivision (I&M Jct.-Madison IL)
Kenosha Subdivision (Chicago-Kenosha)
Kenosha Subdivision (Kenosha-Milwaukee)
New Line Subdivision (Proviso Yard-Milwaukee)
Farm Subdivision (Kenosha-Rockford)
Air Line Subdivision (Milwaukee-Fond Du Lac)
Harvard Subdivision (Chicago-Harvard)
Harvard Subdivision (Harvard-Janesville-Evanville)
Madison Subdivision (Evansville-Elroy-Sparta)
Beloit Subdivision/Footville Subdivision
Adams Subdivision (Milwaukee-Wyeville)
Winona Subdivision (Wyeville-Winona)
Waukesha Subdivision (Milwaukee-Madison)
Clyman Subdivision (Janesville-Fond Du Lac)
Valley Subdivision (Fond Du Lac-Green Bay)
Wisconsin Rapids Subdivision (Fond Du Lac-Marshfield)
Shoreline Subdivision (Milwaukee-Green Bay)
Shawano Subdivision (Green Bay-Eland)
Wausau Subdivision (Eland-Marshfield)
Rhinelander Subdivision (Antigo-Ashland)
Wyeville Subdivision (Elroy-Altoona)
Altoona Subdivision (Altoona-Eau Claire-St. Paul)
Spooner Subdivision (Eau Claire-Spooner)
New Richmond Subdivision (Northline-Spooner)
11th & 12th Districts (Keithsburg-Peoria)