S.D. Codified Laws § 49-16A-41
If freight is delivered to a railroad for transportation to a point of destination, between which and the point of delivery two or more published through routes and through rates have been established pursuant to this chapter, and to which through routes and through rates the railroad is a party, the person making the shipment may designate in writing by which of such routes the freight shall be transported to its destination. Thereupon it is the duty of the initial railroad to route such freight and issue a through bill of lading as directed, and to transport such freight over its own line or lines and deliver the same to a connecting line or lines according to such through route. Each of the connecting railroads shall receive such freight and transport it over the designated line or lines and deliver it to the next succeeding carrier or consignee according to the routing instructions in the bill of lading. The shipper shall in all instances have the right to determine, where competing lines of a railroad constitute portions of a through line or route, over which of the competing lines his freight shall be transported.
SDCL 49-16A-41