S.D. Codified Laws § 51A-4-26
A bank may, without limitation as to capital stock and surplus, purchase bonds, notes, debentures, or other obligations issued by or the payment of which is guaranteed by the United States government or any agency or subdivision thereof, including the Federal Home Loan Mortgage Corporation, Federal Agricultural Mortgage Corporation, the State of South Dakota, any state, territorial, or insular possession of the United States, any county, rural district, school district, municipality, or township of the State of South Dakota, or any out-of-state county, municipality, or political subdivision, if such bonds, notes, debentures, or obligations are general obligations of the issuing authority. A bank may, without such limitation purchase state, municipal, or school district subdivision bonds or notes which are fully defeased as to principal and interest and may also purchase bonds or interim notes issued by the South Dakota Building Authority. The Banking Commission may by rule grant additional investment exceptions, if such additional investments are the general obligation of the issuing authority. A bank may purchase stock in the Federal Agricultural Mortgage Corporation established under Title VII of the Agricultural Credit Act of 1987 (P.L. 233).
SDCL 51A-4-26