1. The portion of Interstate Highway 70 from the western city limits of a city not within a county and proceeding east to mile marker 248 shall be designated the "Mark Twain Highway".
2. The portion of Interstate Highway 70 contained within a city not within a county, from mile marker 248 to the Illinois border, shall be designated the "Andy Gammon Memorial Highway". The department of transportation shall erect and maintain appropriate signs designating such highway, with the costs for such designation to be paid for by private donations.