2010 South Dakota Code
Title 31 - HIGHWAYS AND BRIDGES
Chapter 04 - State Trunk Highway System
Section 31-4-132 - U.S. Highway 12 from North Dakota to Minnesota.

31-4-132. U.S. Highway 12 from North Dakota to Minnesota. The state trunk highway system includes the following in Perkins, Corson, Walworth, Edmunds, Brown, Day, Roberts, and Grant counties:
From the North Dakota state line on the north line of section twenty-one, township twenty-three north, range fourteen east, thence easterly via Lemmon, Morristown, McIntosh, McLaughlin, Mobridge, Selby, Bowdle, Roscoe, Ipswich, Aberdeen, Groton, Bristol, Webster, Waubay, Milbank, and Big Stone City to the Minnesota state line near the east quarter corner of section seventeen, township one hundred twenty-one north, range forty-six west.

Source: SL 1984, ch 209, § 5.