Mo. Rev. Stat. § 506.280

The foregoing provisions relative to service of process in suits against nonresidents shall not be deemed to prevent actual personal service in this state upon a nonresident in the time, manner, form, or under the conditions provided for service on residents, and nothing contained in sections 506.200 to 506.320 shall be construed as in any manner limiting, affecting or repealing any cause of action, right, or method of procedure now provided by law, but the provisions of said sections are cumulative and in addition to any such existing right, remedy, cause of action, and method of procedure.