S.D. Codified Laws § 7-1-41
Beginning at a point on the boundary line between the states of South Dakota and Wyoming ten miles north of the point where the forty-fourth parallel of north latitude intersects the said boundary line, thence due east in a direct line to a point where said line intersects the range line between ranges five and six east Black Hills meridian; thence north and along the range line between ranges five and six east, to the township line between townships three and four north, Black Hills base line; thence west and along said township line to the range line between ranges four and five east Black Hills meridian; thence north and along the range line between said ranges four and five to the township line between townships seven and eight north; thence west and along the township line between said townships seven and eight to the point where said line intersects the center of the main channel of Redwater Creek; thence westerly and along the center of the channel of said Redwater Creek to the said boundary line between the states of South Dakota and Wyoming; thence south and along said state line to the place of beginning.
SDCL 7-1-41