Yellowstone Trail

Cut into the hillside above I-90 is the Yellowstone Trail, prehistorically established by Plateau groups traveling to the Great Plains. This was the first highway through North Idaho and was built between 1914 and 1916. It followed much of the same route as the Mullan Road, In 1926 the Yellowstone Trail was renamed U.S. Highway 10 and then in the 1960s and 1970s was redesignated in various sections as I-90.