Mo. Rev. Stat. § 72.160

Whenever a petition containing the signatures of one hundred voters, or fifteen percent of the total number of votes cast in the last preceding election, whichever is greater, in each of the affected municipalities (provided, however, that in the event any affected municipality has a population of less than one thousand the one hundred or more minimum signature requirement shall not apply, and only the fifteen percent requirement shall apply as to such municipality) shall petition the county commission to order the question of consolidation of such cities, towns or villages into one city, town or village, the county commission at the next regular or special term of said commission shall submit the question to the voters.