S.D. Codified Laws § 31-10-6

The department may not purchase, acquire by condemnation, or construct any bridge under the provisions of §§ 31-10-2 to 31-10-11, inclusive, until such time as the adjoining and contracting state furnishes its proportionate share of the purchase price or cost of construction, or signify its intention, by and through its proper department, of acquiring title through the exercise of the power of eminent domain of the portion of any existing bridge situate in the adjoining state.