Mo. Rev. Stat. § 443.310: Sales, where made — number of days' notice.

All sales of real estate under a power of sale contained in any mortgage or deed of trust executed after August 28, 1989, shall be made in the county where the land to be sold is situated, and not less than twenty days' notice of such sale shall be given, whether so provided in such mortgage or deed of trust or not. Where the property to be sold is located in more than one county, the property may be sold in any county where a part of the property is located.