SDCL § 7-1-9: Buffalo County boundaries.

Beginning at the northeast corner of township one hundred eight north of range sixty-eight, west of the fifth principal meridian, thence west and along the second standard parallel north, to the center of the main channel of the Missouri River; thence southerly and down the center of the main channel of said Missouri River to the township line between townships one hundred five and one hundred six north; thence east and along said township line to the southeast corner of township one hundred six north of range sixty-eight west; thence north and along the range line between ranges sixty-seven and sixty-eight west, to the place of beginning.