Mo. Rev. Stat. § 525.300

Wages earned out of this state, and payable out of this state, shall be exempt from garnishment in aid of attachment in all cases where the cause of action arose or accrued out of this state, unless the defendant in the attachment suit is personally served with process; and if the writ of attachment is not personally served on the defendant, the court issuing the writ of attachment shall not entertain jurisdiction of the cause, but shall dismiss the suit at the cost of plaintiff. In all actions commenced in this state in which it is sought to garnish wages in aid of attachment, the petition or statement filed in such cause and the writ of attachment shall affirmatively show the place where the defendant resides and the place where the debt is contracted and the cause of action arose.