The Mutual Aid Box Alarm System organization has divided the state into 3 regions: Northern Illinois, Central Illinois, and Southern Illinois.  The divisions are not based entirely on county lines.  The City of Chicago is its own MABAS Division

Boone County

Carroll County

Cook County

City of Chicago

DeKalb County

DuPage County

Grundy County

Jo Daviess County

Kane County

Kankakee County

Kendall County

Lake County

Lee County

McHenry County

Ogle County

Stephenson County

Whiteside County

Will County

Winnebago County