Mo. Const. art. III, § 5
Mo. Const. art. III, § 5. Senators — number — senatorial districts
The senate shall consist of thirty-four members elected by the qualified voters of the senatorial districts for a term of four years. Senatorial districts shall be apportioned as provided for in Article III, Section 7. [Effective - 06 Dec 2018, 2 histories , see footnote]