Mo. Rev. Stat. § 249.020
249.020 Determination of population.
249.020. Determination of population. — The last preceding federal census shall be used as a basis and for the purposes of ascertaining and determining the population of the counties that may come within the provisions of sections 249.010 to 249.420 .
(RSMo 1939 § 12680) CROSS REFERENCE: United States census, effective date of, 1.100