S.D. Codified Laws § 7-1-54
Beginning at the southeast corner of township one hundred seventeen north of range seventy-three, west of the fifth principal meridian, thence north and along the range line between ranges seventy-two and seventy-three west, to the northeast corner of township one hundred twenty, north of range seventy-three; thence west and along the township line between townships one hundred twenty and one hundred twenty-one north, to the center of the main channel of the Missouri River; thence down and along the center of the main channel of the Missouri River to its intersection with the township line between townships one hundred sixteen and one hundred seventeen, north; thence east and along the said township line to the place of beginning.
SDCL 7-1-54