Mo. Rev. Stat. § 65.692
The regulations imposed and the districts created under authority of sections 65.650 to 65.700 may be amended from time to time by the township board by order after the order establishing the same has gone into effect but no such amendment shall be made by the township board except after recommendation of the township planning commission, or if there is no township planning commission, of the township zoning commission, after hearings thereon by such commission. Public notice of such hearings shall be given in the same manner as provided for the hearing in section 65.662. In case of written protest against any proposed change or amendment, signed and acknowledged by the owners of thirty percent of the frontage within one thousand feet to the right or left of the frontage proposed to be changed, or by the owners of thirty percent of the frontage directly opposite, or directly in the rear of the frontage proposed to be altered, or in cases where the land affected lies within one and one-half miles of the corporate limits of a municipality having in effect ordinances zoning property within the corporate limits of such municipality, made by resolution of the city council or board of trustees thereof, and filed with the township clerk, such amendment may not be passed except by the favorable vote of all the members of the township board.
§ 65.692, RSMo