The 40th Legislative District contains portions of the southland as well as a majority of Kankakee County, an eastern portion of Will County and southeastern Grundy County.

County Government:

Cook
Grundy
Kankakee
Will 

City, Town & Village Government:

Bonfield
Bourbonnais
Braceville
Bradley
Braidwood
Buckingham
Chebanse
Chicago Heights
Crete
Custer Park
East Brooklyn
 
Essex
Flossmoor
Frankfort
Herscher
Kankakee
Limestone
Manhattan
Manteno
Matteson
Mokena
Monee
 
New Lenox
Olympia Fields
Park Forest
Reddick
Richton Park
South Chicago Heights
South Wilmington
Steger
Symerton
University Park
Wilmington