65 ILCS 5/5-2-4

Except as otherwise provided in Section 5-2-3, every city shall have one-half as many wards as the total number of alderpersons to which the city is entitled. The city council, from time to time shall divide the city into that number of wards. In the formation of wards the population of each shall be as nearly equal, and the wards shall be of as compact and contiguous territory, as practicable.