The Missouri portion of the bridge on Interstate 55, Interstate 64, Interstate 70, and U.S. Route 40 crossing the Mississippi River between downtown St. Louis and southwestern Illinois, commonly known as the Poplar Street Bridge, shall be designated the “Congressman William L. Clay, Sr. Bridge”. The department of transportation shall erect and maintain appropriate signs designating the Missouri portion of such bridge, with the costs for such designation to be paid for by private donation. The designation under this section shall supersede any prior name or designation for such bridge.