Mo. Rev. Stat. § 321.687
In any county of the first class with a charter form of government containing a population of nine hundred thousand or more, if two or more fire districts consolidate as prescribed by sections 321.460 to 321.470, the new board of directors will consist of five members. If, upon canvass and declaration, it is found and determined that a majority of the voters of the districts voting on the propositions have voted in favor of the proposition to incorporate the consolidated district, then the court shall then further, in its order, designate the first board of directors of the consolidated district, who have been elected by the voters voting thereon as follows: The one receiving the fifth highest number of votes to hold office for a term of at least one year, the one receiving the fourth highest number of votes to hold office for a term of at least two years, the one receiving the third highest number of votes to hold office for a term of at least three years and the two receiving the second and first highest number of votes to hold office for a term of at least four years from the date of the election of the board of directors and until their successors are duly elected and qualified. Thereafter, members of the board shall be elected to serve terms of four years and until their successors are duly elected and qualified.
§ 321.687, RSMo