55 ILCS 5/2-3004
If any county board fails to complete the reapportionment of its county by July 1 in 2011 or any 10 years thereafter or by the day after the county board's regularly scheduled July meeting in 2011 or any 10 years thereafter, or for the reapportionment of 2021, by December 31 in the year after a federal decennial census year, whichever is later, the county clerk of that county shall convene the county apportionment commission. Three members of the commission shall constitute a quorum, but a majority of all the members must vote affirmatively on any determination made by the commission. The commission shall adopt rules for its procedure.
The commission shall develop an apportionment plan for the county in the manner provided by Section 2-3003, dividing the county into the same number of districts as determined by the county board. If the county board has failed to determine the size of the county board to be elected, then the number of districts and the number of members to be elected shall be the largest number to which the county is entitled under Section 2-3002.
The commission shall submit its apportionment plan by October 1 in the year that it is convened, or for the reapportionment of 2021, by February 1, 2022, except that the circuit court, for good cause shown, may grant an extension of time, not exceeding a total of 60 days, within which such a plan may be submitted.
55 ILCS 5/2-3004