Iowa Code § 321.345: Stop or yield at highways.

The department, based on an engineering study, with reference to primary highways, and local authorities with reference to other highways under their jurisdiction may designate through highways and erect stop signs or yield signs, in accordance with specifications established by the department at specified entrances to the highway or may designate any intersection as a stop intersection or as a yield intersection and erect like signs at one or more entrances to such intersection.