Mo. Rev. Stat. § 128.010: Electoral districts — number of electors to be chosen.

Hereafter, at all elections held in this state for the offices of president and vice president of the United States, the electoral district shall be the same as the congressional districts into which the state shall be divided, and the same number of electors as there may be districts shall be chosen by the qualified voters, one of whom shall be a resident of each district; and in addition thereto, two electors shall be chosen by the state at large.