Mo. Rev. Stat. § 211.291: Juvenile courtroom in counties of first and second class — any judge of circuit may hold court, when.

1. In counties of the first and second class and in the city of St. Louis a courtroom, to be designated the juvenile courtroom, shall be provided by the county or circuit court of the county or city, as the case may be, for the hearing of cases under this chapter.

2. In case of the absence or inability of the judge of the juvenile court in any such county to hold court, any one of the circuit judges in the judicial circuit may perform that duty.