Mo. Rev. Stat. § 432.070: Contracts, execution of by counties, towns — form of contract.

No county, city, town, village, school township, school district or other municipal corporation shall make any contract, unless the same shall be within the scope of its powers or be expressly authorized by law, nor unless such contract be made upon a consideration wholly to be performed or executed subsequent to the making of the contract; and such contract, including the consideration, shall be in writing and dated when made, and shall be subscribed by the parties thereto, or their agents authorized by law and duly appointed and authorized in writing.