S.D. Codified Laws § 9-27-31
If any municipality owns land which is suitable for a site upon which to build a courthouse for the county in which such municipality is located, and the county seat of such county has been permanently located in such municipality, fifteen percent of the registered voters of such municipality, based upon the total number of registered voters at the last preceding general election, may petition that the question of donating such site to the county for a courthouse building site be submitted to a vote of the municipality. The petition shall be filed with the municipal finance officer twenty days before the election. The governing body shall submit the proposition to the voters of such municipality either at the annual municipal election or at a special election called for that purpose.
The question shall be submitted on a separate ballot, which shall be in the form and which shall be cast in the manner provided by chapter 9-13.
SDCL 9-27-31