Mo. Rev. Stat. § 516.155: Mortgages last maturing obligation is due, how determined — future advances on real property security instrument statute begins to run, when.

1. Except as provided in subsection 2 of this section, whenever under the provisions of section 516.150 "the date at which the last maturing obligation secured by the instrument sought to be foreclosed is due on the face of such instrument" cannot be determined from the face of such instrument, the twenty-year period referred to in section 516.150 shall begin to run on the recited date of execution of such instrument, or if there is no recited date, the date of acknowledgment of such instrument, or if there is neither a recited date of execution nor a date of acknowledgment, the date of recording of such instrument, or if there is none of the above, the original date of the secured obligation, except that the provisions of this subsection shall apply only to deeds of trust and mortgages recorded after January 1, 1979.

2. In the case of a security instrument described in section 443.055, the twenty-year period referred to in section 516.150 shall begin to run on the twentieth anniversary of the recited date of execution of such security instrument, or if there is no recited date, the date of acknowledgment of such security instrument, or if there is neither a recited date of execution nor a date of acknowledgment, the date of recording of such instrument, except that the provisions of this subsection shall apply only to such security instruments recorded after September 1, 1992.