Mo. Rev. Stat. § 525.290

No wages shall be garnished in aid of attachment before personal service is had or obtained upon the defendant, unless the suit be brought in the county where the defendant resides, or in the county where the debt is contracted and the cause of action arose or accrued, and in cities over one hundred thousand inhabitants in the city where the defendant resides or the debt is contracted and the cause of action accrued; provided, the petition or statement filed in the cause and 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.