Wyo. Stat. § 15-11-103
The elective officers of a first class city, not including a city adopting the commission or city manager form of government, are a mayor and the number of councilmen determined by the governing body of the city when they provide for the number of wards in the city. The term of office of the mayor and a councilman is four (4) years and until his successor is qualified. The mayor shall be elected at large and the councilmen shall be elected at large or by wards or by a combination of at large and ward election districts. The governing body of the city shall determine by ordinance at the time wards are created or reorganized whether individual, multimember or at large election districts shall be provided. The districting system, as approved by the council to apply uniformly to the entire city, may provide individual member election districts, multimember election districts which do not exceed three (3) council members per district, or that a portion of the entire membership of the council not to exceed one-third (1/3) of the total members shall be elected from an at large district constituting the entire city. Once established, the districts, except to modify boundaries because of population changes and to encompass annexed territory, shall not be altered or amended more often than each ten (10) years or when the state reapportions.
W.S. 15-11-103