SDCL § 31-4-139: U.S. Highway 16 Alternate from U.S. Highway 16 at Custer via Keystone to U.S. Highway 16.

The state trunk highway system includes the following in Custer and Pennington counties:

From a point on U.S. Highway 16 in Custer near the northeast corner of section twenty-six, township three south, range four east, thence easterly and northerly via Custer and Keystone to U.S. Highway 16 north of Keystone on the north line of section thirty-one, township one south, range six east.