South Dakota Probate Records
From Ancestry.com Wiki
Wills and intestate proceedings originate at the county in which the deceased lived, usually at the county clerk of the court’s office. Some have been transferred to the state archives at the Cultural Heritage Center, cataloged under Unified Judicial System, Circuit Courts, Division of [County name] County (see South Dakota Court Records).
Many probate records for Indian agencies have been microfilmed and are available through The Family History Library (FHL). Those that have not will be available through the National Archives (see Native Americans of South Dakota).