Mo. Rev. Stat. § 78.470: Candidates may be nominated by primary election, exception.

Except as provided in section 78.530, candidates to be voted for at all general and special municipal elections at which the officers are to be elected under the provisions of sections 78.430 to 78.640 shall be nominated by a primary election, and no other names shall be placed upon the general ballot except those nominated as herein prescribed. The primary for such nominations shall be held on the first Tuesday after the first Monday in February preceding the election, and the judges of the election appointed for general or special election shall be the judges of the primary election, so far as possible.