Mo. Rev. Stat. § 55.060
No person shall be elected or appointed county auditor of a county of the first class not having a charter form of government or of a county of the second class unless he is a citizen of the United States above the age of twenty-one years, and has resided within the state for one whole year and within the county for which he is elected or appointed for three months immediately preceding the election or his appointment. He shall also be a person familiar with the theory and practice of accounting by education, training and experience and able to perform the duties imposed upon the county auditor by the provisions of this chapter. The county auditor shall, after his appointment or election, reside in the county for which he is auditor.
§ 55.060, RSMo