S.D. Codified Laws § 31-28-1
Current with legislation signed by the governor on or before 3/6/2024
The Department of Transportation shall keep the various lines of highways comprising the state trunk highway system, including the connecting streets in municipalities, distinctly marked with some standard design placed on convenient objects along the routes. The design shall be uniform on all parts of the trunk highway system. However, the numbers shall correspond with the numbers given the various routes by the department. The numbers shall coincide with the numbers placed on the official map or maps issued by the department. No similar design may be used for marking other routes in South Dakota.
SDCL 31-28-1