Mo. Rev. Stat. § 153.010: Express company defined.

Any person, persons, joint stock association, company or corporation incorporated under the laws of any state, territory or country, conveying to, from or through this state, or any part thereof, money, packages, gold, silver, plate, articles, goods, merchandise or effects of any kind by express, on contract with any railroad or steamboat company, or the managers, lessees, agents or receiver thereof, not including railroad companies or steamboats engaged in the ordinary transportation of merchandise and property in this state, shall be deemed to be an "express company" .