Constitution of the State of Illinois Art. VII, § 3. County Boards

(a) A county board shall be elected in each county. The number of members of the county board shall be fixed by ordinance in each county within limitations provided by law.

(b) The General Assembly by law shall provide methods available to all counties for the election of county board members. No county, other than Cook County, may change its method of electing board members except as approved by county-wide referendum.

(c) Members of the Cook County Board shall be elected from two districts, Chicago and that part of Cook County outside Chicago, unless (1) a different method of election is approved by a majority of votes cast in each of the two districts in a county-wide referendum or (2) the Cook County Board by ordinance divides the county into single member districts from which members of the County Board resident in each district are elected. If a different method of election is adopted pursuant to option (1) the method of election may thereafter be altered only pursuant to option (2) or by county-wide referendum. A different method of election may be adopted pursuant to option (2) only once and the method of election may thereafter be altered only by county-wide referendum.