S.D. Codified Laws § 31-29-70
An "unzoned commercial or industrial area," in consideration of the advertising needs of remote rural businesses located outside of municipal corporate limits, shall mean the areas adjacent to an interstate or primary highway within this state which are not zoned by state or local law, regulation, or ordinance, and on which there is located one or more permanent structures devoted to a commercial or industrial activity or on which a commercial or industrial activity is actually conducted, whether or not a permanent structure is located thereon, and the area along the highway extending outward one thousand feet from and beyond the edge of each side of the activity. Each side of the highway shall be considered separately in applying this definition. All measurements shall be from the outer edges of the regularly used buildings, parking lots, storage, or processing and landscaped areas of the commercial or industrial activities, not from the property lines of the activities, and shall be along or parallel to the edge of pavement of the highway. The cessation of the commercial or industrial activity shall terminate the designation of an area as an "unzoned commercial or industrial area" after six months, at which time outdoor advertising therein shall become nonconforming.
SDCL 31-29-70