Highway 18. The state trunk highway system includes the following in Fall River County: From a point on State Highway 71 north of Ardmore near the southeast corner of section eight, township eleven south, range four east, thence northwest via Edgemont to a point on U.S. Highway 18 in Edgemont in the southwest quarter of section thirty - six, township eight south, range two east. Source: SL 1984, ch 209 , § 117.