Mo. Rev. Stat. § 54.040
Except in a county with a charter form of government, a candidate for county treasurer shall be at least twenty-one years of age and a resident of the state of Missouri and the county in which he or she is a candidate for at least one year prior to the date of the general election for such office. The candidate shall also be a registered voter and shall be current in the payment of all personal and real estate taxes. Upon election to such office, the person shall continue to reside in that county during his or her tenure in office. Each candidate for county treasurer shall also provide to the election authority a copy of a signed affidavit from a surety company authorized to do business in this state indicating that the candidate meets the bond requirements for the office of county treasurer under this chapter.
§ 54.040, RSMo