S.D. Codified Laws § 31-13-31
All contracts or agreements of supervisors of organized civil townships, entered into between such supervisors and residents or landowners of such township, whereby such residents or landowners were to perform work, furnish equipment and material in the construction or repair of secondary highways of such township, and whereby such residents or landowners were to be compensated for work performed in the construction and repair of such highways and be reimbursed for funds advanced in the purchase of material or for the use of equipment, are hereby legalized and validated; the board of supervisors of such township is hereby authorized to pay such resident or landowner or cause them to be paid from township funds, for such services performed, compensation for the use of equipment and for materials furnished in the construction or repair of such road and the said board of supervisors is authorized to approve and issue warrants for such payment and to pay or cause such warrants to be paid from township funds. The allowance of such claims for said services performed, materials furnished or for use of equipment and the payment for the same shall be deemed valid and for a lawful purpose. Provided, that the provisions of this section shall apply only to contracts of this kind entered into prior to July 1, 1953, and provided further that where such contracts have been entered into before July 1, 1953, and funds have been expended pursuant to such contracts, such contracts and the funds expended thereunder are hereby legalized and validated.
SDCL 31-13-31