The city clerk and the city treasurer shall be elected at the same time that the mayor is elected, except in the case of an election to fill a mayoral vacancy and except in the case of a city having 10,000 or fewer inhabitants in which, by ordinance, the position of city treasurer is an appointed position. If a vacancy occurs in the office of city clerk or city treasurer, it shall be filled by the mayor with the advice and consent of the city council. The person so appointed shall hold office for the unexpired term of the officer elected.
65 ILCS 5/3.1-20-5