Mo. Rev. Stat. § 65.160
Every person chosen or appointed to the office of township trustee and ex officio treasurer, member of the township board, township collector, or township clerk, before he enters on the duties of his office and within ten days after he shall be notified of his election or appointment, shall take and subscribe, before any officer authorized to administer oaths, such oath or affirmation as is prescribed by law.
(RSMo 1939 § 13954, A.L. 1945 p. 1968, A. 1949 H.B. 2021, A.L. 1981 H.B. 114 & 146)
Prior revisions: 1929 § 12277; 1919 § 13190; 1909 § 11678