S.D. Codified Laws § 21-41-9
The court may grant an order for the service of the summons upon defendants who are unknown, whether heirs, devisees, legatees, personal representatives, or creditors or any other unknown person, by publication upon the filing of an affidavit by the plaintiff, his agent or attorney, stating that if there are any persons other than those named as defendants in the summons and complaint who have or claim to have any interest or estate in or claim to, or lien or encumbrance upon the premises adverse to plaintiff, such persons are unknown. No deposit of a copy of the summons and complaint in the post office for unknown defendants shall be required, and service shall be complete as to all unknown defendants at the expiration of the publication of the summons as ordered and shall be taken and accepted as personal service on all parties unknown who have or claim to have any such interest, estate, claim, lien, or encumbrance in, to, or upon the property described in the complaint.
SDCL 21-41-9