 The first section of the Columbia River section was completed in 1969, but the remainder never left the design phase.SSH 1T became SR 501 during the 1964 highway renumbering and codified as such in 1970, being designated as the Erwin O. Rieger Memorial Highway in 1991.In the late 1990s, Mill Plain Boulevard was extended west from downtown Vancouver to the industrial area west of the railyard to serve the Port of Vancouver.