S.D. Codified Laws § 31-3-41
The legally constituted authorities of any county, township, or municipality in the State of South Dakota are hereby authorized and empowered to enter into contracts with the United States of America fixing the terms and conditions under which the part of any highway or system of highways under the control, jurisdiction, and supervision of any such county, township, or municipality in this state which it is found necessary to relocate, rearrange, or alter in order to facilitate the construction of the dams and reservoirs, within the State of South Dakota, by the United States government in the development of the Missouri River flood control projects will be made. Provided that any such contract entered into shall provide for reimbursement of any such county, township or municipality by the United States of America for all works performed and materials furnished under said contract by any county, township, or municipality.
SDCL 31-3-41