Highway 12 to State Highway 15. The state trunk highway system includes the following in Grant and Roberts counties: From a point on U.S. Highway 12 in Big Stone City in the northwest quarter of section seventeen, township one hundred twenty - one north, range forty - six west, thence northwest to State Highway 15 east of Hartford Beach near the northwest corner of section twelve, township one hundred twenty - two north, range forty - eight west. Source: SL 1984, ch 209 , § 63.