The Illinois developmental disabilities service system is divided into 7 regions. State staff are assigned to each region, and service providers are assigned to these regions based on their geographic area. 

Region Counties Included in Each Region
Northwest Region Boone, Carroll, DeKalb, Jo Daviess, Lee, Ogle, Stephensen, Whiteside, Winnebago
North Suburban Region Cook (Map of Chicago (pdf)), DuPage, Kane, Kendall, Lake, McHenry 
City of Chicago See Map of Chicago (pdf) area for all areas included in this Region
South Suburban Region Cook (Map of Chicago (pdf)), Grundy, Kankakee, Will 
North Central Region Bureau, Champaign, Ford, Fulton, Henderson, Henry, Iroquois, Knox, LaSalle, Livingston, Marshall, Mason, McDonough, McLean, Mercer, Peoria, Piatt, Putnam, Rock Island, Stark, Tazewell, Vermillion, Warren, Woodford 
Central Region Adams, Brown, Calhoun, Cass, Christian, Clark, Coles, Cumberland, DeWitt, Douglas, Edgar, Effingham, Greene, Hancock, Jersey, Logan, Macon, Macoupin, Menard, Montgomery, Morgan, Moultrie, Pike, Sangamon, Schuyler, Scott, Shelby 
Southern Region Alexander, Bond, Clay, Clinton, Crawford, Edwards, Fayette, Franklin, Gallatin, Hamilton, Hardin, Jackson, Jasper, Jefferson, Johnson, Lawrence, Madison, Marion, Massac, Monroe, Perry, Pope, Pulaski, Randolph, Richland, St. Clair, Saline, Union, Wabash, Washington, Wayne, White, Williamson