Mo. Rev. Stat. § 59.160: Office hours, cities of 300,000 or more population.

It shall hereafter be the duty of recorders of deeds, in cities which now have, or may hereafter have, a population of three hundred thousand inhabitants or over to keep their offices open for the transaction of business between the hours of nine o'clock in the morning and five o'clock in the afternoon Monday through Friday, except on days which are now or which may be hereafter declared public holidays by the laws of this state.