16 U.S.C. § 441b
Construction of highway by State of South Dakota
The establishment of said park is conditioned upon the State of South Dakota first constructing the following highway in a manner satisfactory to the Secretary of the Interior: A highway commencing at the corporation limits of the town of Interior, thence going in a northwesterly direction to and over Big Foot Pass, and through the region known as The Pinnacles; thence in a westerly direction to Sage Creek, being a total distance of about thirty miles.