|Description||Counties of the State of Illinois |
There are 102 counties in the State of Illinois. The most populated counties are Cook, DuPage, Lake, Will and Kane. The least dense is Pope, which is also the smallest in acreage.
The oldest county in Illinois is St. Claire founded in 1790. Its seat is Belleville. The newest counties were founded in 1859, Ford and Douglas.
Illinois' counties are organized under the Illinois Association of County Board Members and Commissioners, affiliated with the National Association of Counties. You can contact them through 413 West Monroe Street, 2nd Floor, Springfield, IL 62704-1959, Phone (217)528-5331, Fax (217)528-5562 .