Mo. Rev. Stat. § 474.360: Written will valid if executed in compliance with law.

A written will is valid if executed in compliance with:

(1) The laws of this state;

(2) The laws, as of the time of execution, of the place where the will is executed; or

(3) The laws of the place where, at the time of execution or the time of the testator's death, the testator is domiciled, has a place of abode or is a national.