The portion of Highway A beginning at the intersection of Business Route 60 on the town square in the city of Mansfield and proceeding east to its intersection with Highway K in the city of Macomb, except where otherwise designated, shall be designated the “Laura Ingalls Wilder Memorial Highway” in dedication to the author and her contribution to the state of Missouri. The department of transportation shall erect and maintain appropriate signs commemorating this portion of Highway A at its discretion, and the Laura Ingalls Wilder Museum shall pay for all such signs.