S.D. Codified Laws § 29A-5-108
A petition for the appointment of a guardian or conservator shall be filed in the county in which the minor either resides or is present or, if the minor has been admitted to a facility pursuant to an order of court, in the county in which that court is located. If the minor neither resides in nor is present in this state, a petition for the appointment of a conservator shall be filed in a county in which the minor has property or in the county having jurisdiction of a decedent's estate in which the minor has an interest. The court of the county in which the proceeding is first commenced shall have exclusive jurisdiction to decide the petition unless that court determines that a transfer of venue would be in the best interests of the minor.
SDCL 29A-5-108