S.D. Codified Laws § 1-1-7
If any land in county ownership is desired by the United States for any of the purposes referred to in § 1-1-6, the commissioners of the county in which said land is situated may determine and appraise its value, and may submit a copy of said appraisal to the proper agency or officer of the United States. If the willingness of the United States to pay such appraised value is expressed by appropriate action of the authorized agency or officer, the said lands may be advertised and offered for sale in the manner provided by law; and if no acceptable and satisfactory bid in excess of said appraised value is received, the county commissioners may and they are authorized to sell said lands to the United States upon payment of the appraised and agreed value thereof.
SDCL 1-1-7