(65 ILCS 5/3.1-20-10) (from Ch. 24, par. 3.1-20-10)
    Sec. 3.1-20-10. Aldermen; number.
    (a) Except as otherwise provided in this Section, Section 3.1-20-20, or as otherwise provided in the case of aldermen-at-large, the number of aldermen, when not elected by the minority representation plan, shall be determined using the most recent federal decennial census results as follows:
        (1) in cities not exceeding 3,000 inhabitants, 6
    
aldermen;
        (2) in cities exceeding 3,000 but not exceeding
    
15,000, 8 aldermen;
        (3) in cities exceeding 15,000 but not exceeding
    
20,000, 10 aldermen;
        (4) in cities exceeding 20,000 but not exceeding
    
50,000, 14 aldermen;
        (5) in cities exceeding 50,000 but not exceeding
    
70,000, 16 aldermen;
        (6) in cities exceeding 70,000 but not exceeding
    
90,000, 18 aldermen; and
        (7) in cities exceeding 90,000 but not exceeding
    
500,000, 20 aldermen.
    (b) Instead of the number of aldermen set forth in subsection (a), a municipality with 15,000 or more inhabitants may adopt, either by ordinance or by resolution, not more than one year after the municipality's receipt of the new federal decennial census results, the following number of aldermen: in cities exceeding 15,000 but not exceeding 20,000, 8 aldermen; exceeding 20,000 but not exceeding 50,000, 10 aldermen; exceeding 50,000 but not exceeding 70,000, 14 aldermen; exceeding 70,000 but not exceeding 90,000, 16 aldermen; and exceeding 90,000 but not exceeding 500,000, 18 aldermen.
    (c) Instead of the number of aldermen set forth in subsection (a), a municipality with 40,000 or more inhabitants may adopt, either by ordinance or by resolution, not more than one year after the municipality's receipt of the new federal decennial census results, the following number of aldermen: in cities exceeding 40,000 but not exceeding 50,000, 16 aldermen.
    (d) If, according to the most recent federal decennial census results, the population of a municipality increases or decreases under this Section, then the municipality may adopt an ordinance or resolution to retain the number of aldermen that existed before the most recent federal decennial census results. The ordinance or resolution may not be adopted more than one year after the municipality's receipt of the most recent federal decennial census results.
(Source: P.A. 96-1156, eff. 7-21-10; 97-301, eff. 8-11-11; 97-1091, eff. 8-24-12.)