65 ILCS 5/3.1-20-25
2021 Illinois Compiled Statutes|Chapter 65 - MUNICIPALITIES|65 ILCS 5/ - Illinois Municipal Code.|Article 3.1 - Officers

 (from Ch. 24, par. 3.1-20-25)Sec. 3.1-20-25. Redistricting a city.(a) In the formation of wards, the number of  inhabitants of the city  immediately preceding the division of the city into wards shall be  as nearly equal in population, and the wards shall be of as compact and  contiguous territory, as practicable. Wards shall be created in a  manner so that, as far as practicable, no precinct shall be divided between  2 or more wards.(b) Whenever an official  decennial census shows that a city contains more or fewer wards than it is  entitled to, the city council of the city, by ordinance, shall redistrict  the city into as many wards as the city is entitled.  This  redistricting shall be completed not less than 30 days before the first day  set by the general election law for the filing of candidate petitions for  the next succeeding election for city officers.  At this election there  shall be elected the number of alderpersons to which the city is entitled,  except as provided in subsection (c).(c) If it appears from any official decennial census  that it is necessary to redistrict under subsection (b) or for any other reason, the city council shall  immediately proceed to redistrict the city  and shall hold the next city election in  accordance with the new redistricting. At this election the alderpersons whose  terms of office are not expiring shall be considered alderpersons for the new  wards respectively in which their residences are situated.  At this election, in a municipality that is not a newly incorporated municipality, a  candidate for alderperson may be elected from any ward that contains a part of the ward in which he or she resided  at least one year next preceding the election that follows the redistricting,  and, if elected, that person may be reelected from the new ward he or she represents if he or she  resides in that ward for at least one year next preceding reelection. If there are 2  or more alderpersons with terms of office not expiring and residing in the same  ward under the new redistricting, the alderperson who holds over for that ward  shall be determined by lot in the presence of the city council, in the  manner directed by the council, and all other alderpersons shall fill  their unexpired terms as alderpersons-at-large. The alderpersons-at-large, if any,  shall have the same powers and duties as all other alderpersons, but upon the  expiration of their terms the offices of alderpersons-at-large shall be abolished.(d) If the redistricting results in one or more wards in which no alderpersons   reside whose terms of office have not expired, 2 alderpersons shall be elected  in accordance with Section 3.1-20-35, unless the city elected only one alderperson   per ward pursuant to a referendum under subsection (a) of Section  3.1-20-20.(e) A redistricting ordinance that has decreased the number  of wards of a city because of a decrease in population of the city shall  not be effective if, not less than 60 days before the time fixed for  the next succeeding general municipal election, an official  census is officially published that shows that the city has regained a  population that entitles it to the number of wards that it had just  before the passage of the last redistricting ordinance.   (Source: P.A. 102-15, eff. 6-17-21.)