S.D. Codified Laws § 31-28-2
Current with legislation signed by the governor on or before 3/6/2024
If, in the marking or numbering of any state trunk highway, there is a division of the highway into two branches, there shall be erected along each of the highways at the initial point of separation a directional sign indicating the general direction or course of the respective highways as to whether the course of the highway is east, west, north, or south as the case may be.
SDCL 31-28-2