Mo. Rev. Stat. § 128.346
The districts established by the provisions of sections 128.400 to 128.440 for the election of representatives to the Congress of the United States shall be effective beginning with election to the 108th Congress.
(L. 1991 S.B. 369 § 1, A.L. 2001 H.B. 1000, A.L. 2007 S.B. 613 Revision)