S.D. Codified Laws § 32-10-2

It is the policy of this state to promote and encourage the fullest possible use of its highway system by authorizing the making and execution of motor vehicle reciprocal or proportional registration agreements, arrangements, and declarations with other states, provinces, territories, and countries with respect to vehicles registered in this and such other states, provinces, territories, and countries thus contributing to the economic and social development and growth of this state.