In all commission-governed municipalities employing a city manager the number of commissioners shall be nine, whose terms of office shall be three years. At the first election thereof there shall be elected nine commissioners, three to serve until the next annual election, three to serve until the second annual election thereafter, three to serve until the third annual election thereafter, and thereafter at each annual municipal election there shall be elected three commissioners for a term of three years each.
SDCL 9-10-5