Mo. Rev. Stat. § 79.025

No city of the fourth classification with more than two thousand three hundred but fewer than two thousand four hundred inhabitants and located in any county with a charter form of government and with more than one hundred ninety-eight thousand but fewer than one hundred ninety-nine thousand two hundred inhabitants shall annex any territory adjacent to the city if such adjacent territory proposed for annexation does not contain any registered voters unless the city has obtained the written consent of all the owners of real property within such adjacent territory.