Mo. Rev. Stat. § 115.577: Time in which election contest may be filed.

Not later than thirty days after the official announcement of the election result by the election authority, any person authorized by section 115.553 who wishes to contest the election for any office or on any question provided in section 115.575 shall file a verified petition in the office of the clerk of the appropriate circuit court. The contestant shall only be required to file one petition with the circuit court for each election contest regardless of the number of counties within the court's jurisdiction. The petition shall set forth the points on which the contestant wishes to contest the election and the facts he will prove in support of such points, and shall pray leave to produce his proof. The circuit court in which the petition is filed shall have exclusive jurisdiction over all matters relating to the contest and may issue appropriate orders to all election authorities in the area in which the contested election was held.