The portion of United States highway 24 from its junction with United States highway 59 north of the city of Williamstown, then southeast to its junction with United States highway 40 north of the city of Lawrence, is hereby designated as the trooper Maurice R. Plummer memorial highway. The secretary of transportation shall place highway signs along the highway right-of-way at proper intervals to indicate that the highway is the trooper Maurice R. Plummer memorial highway.