Mo. Rev. Stat. § 89.420: Commission to approve plats, when.

Within sixty days after the submission of a plat to the commission, the commission shall approve or disapprove the plat; otherwise the plat is deemed approved by the commission, except that the commission, with the consent of the applicant for the approval, may extend the sixty-day period. The ground of disapproval of any plat by the commission shall be made a matter of record.