Mo. Rev. Stat. § 452.150
The father and mother living apart are entitled to an adjudication by the circuit court as to their powers, rights and duties in respect to the custody and control and the services and earnings and management of the property of their unmarried minor children without any preference as between the said father and mother, and neither the father nor the mother has any right paramount to that of the other in respect to the custody and control or the services and earnings or of the management of the property of their said unmarried minor children; pending such adjudication the father or mother who actually has the custody and control of said unmarried minor children shall have the sole right to the custody and control and to the services and earnings and to the management of the property of said unmarried minor children.
§ 452.150, RSMo