S.D. Codified Laws § 31-28-13
Local authorities in their respective jurisdictions may cause appropriate signs to be erected and maintained, designating residence and business districts, highway and steam or interurban railway grade crossing, and such other signs as may be deemed necessary to carry out the provisions of chapters 32-14, 32-22, and 32-25 to 32-31, inclusive, and such additional signs as may be appropriate to give notice of local parking and other special regulations. Local parking and other special regulations shall not be enforceable against an alleged violator if, at the time and place of the alleged violation, an appropriate sign giving notice thereof is not in proper position and sufficiently legible to be seen by an ordinarily observant person.
SDCL 31-28-13