S.D. Codified Laws § 7-1-68
Beginning at the northeast corner of township seventeen north of range twenty-one, east of the Black Hills meridian, thence west and along the township line between townships seventeen and eighteen north, to the one hundred second meridian of west longitude; thence south and along said meridian to the center of the main channel of the Cheyenne River; thence easterly and along the center of the main channel of said Cheyenne River to its intersection with the sixth guide meridian, east, being the range line between ranges twenty-four and twenty-five, east Black Hills meridian; thence north and along said guide meridian to its intersection with the forty-fifth parallel of north latitude; thence west and along said parallel to its intersection with the range line between ranges twenty-one and twenty-two, east; thence north and along said range line to the place of beginning.
SDCL 7-1-68