SDCL § 31-17-2: Roads crossing county lines--Division of responsibility.

Subject to approval of the department, boards of county commissioners of adjoining counties shall make proper connections between roads which cross county lines and which afford continuous routes of travel; adopt plans and specifications for highway construction, reconstruction, and repairs upon highways along and across county boundary lines, and make an equitable division between such counties of the cost and work of execution of such plans and specifications. In case of disagreement on the division, the Transportation Commission shall make the division.