Mo. Rev. Stat. § 81.250: Numbering wards — territory (cities of 20,000 and less than 250,000).

All wards which may hereafter be established shall be composed of adjacent and compact territory, and the several wards at the time of redistricting shall contain as nearly an equal number of inhabitants as may be practicable. The wards shall be numbered consecutively from one up to the highest number thus established.