SDCL § 32-25-9.1: Establishment of speed zones by county commissioners--Posting of zones.

Any board of county commissioners may determine and establish speed zones upon all or any part of the highways under its jurisdiction and upon streets and highways on the request of and after any other local authority, including any road district, having charge of the maintenance of the highway has declared its intention to post speed zones. Such speed zones shall be conspicuously posted at the beginning and ending of the zones.