65 ILCS 5/5-2-19
In any city which was operating under the alderperson form of government as provided in Article 3 at the time of adoption of this Article 5 which did not also elect to continue to choose alderpersons from wards, the city clerk and city treasurer shall be nominated and elected in the same manner as provided in this Article 5 for the nomination and election of the mayor and councilmen. To achieve this result: wherever the term "mayor or commissioners" appears in Sections 4-3-7 through 4-3-18, it shall be construed to include the words "or clerk or treasurer". The names of candidates for nomination shall be placed on the primary election ballot prescribed in Section 5-2-13 and such ballot shall be modified to include the heading "For Clerk--Vote for one" immediately following the names of candidates for councilmen and to include the heading "For Treasurer--Vote for one" immediately following the names of candidates for clerk. The names of the 4 candidates receiving the highest number of votes for each of the respective offices shall be placed on the general municipal election ballot prescribed in Section 5-2-13 which ballot shall be modified to include such offices and names in the same manner as is provided in this section for the primary ballot. If any candidate nominated for the office of clerk or treasurer dies or withdraws before the general municipal election the name of the person receiving the fifth highest number of votes for nomination to that office shall be placed on the ballot for that election.
However, in any city not exceeding 100,000 inhabitants which adopts this Article 5 and elects a mayor and alderpersons or councilmen as provided in Section 5-2-12, or Sections 5-2-18 through 5-2-18.8, the council may, in lieu of electing a clerk and treasurer as provided in the above paragraph, provide by ordinance that the clerk or treasurer or both for such city be appointed by the mayor with the approval of the city council. If such officers are appointed their terms of office, duties, compensation and amount of bond required shall be the same as if they were elected.
65 ILCS 5/5-2-19