Mo. Rev. Stat. § 21.110
Current with changes from the 2024 Legislative Session
If the governor receives any resignation or notice of vacancy, or if he is satisfied of the death of any member of either house, during the recess, he shall, without delay, issue a writ of election to supply the vacancy.
§ 21.110, RSMo
RSMo 1939 § 12859, A.L. 1957 p. 595