 When the Interstate Highway system was in the planning stages , the western terminus of I @-@ 70 was proposed to be at Denver . The portion west of Denver was included into the plans after lobbying by Governor Edwin C. Johnson , for whom one of the tunnels along I @-@ 70 is named . East of Idaho Springs , I @-@ 70 was built along the corridor of U.S. Highway 40 , one of the original transcontinental U.S. Highways . West of Idaho Springs , I @-@ 70 was built along the route of U.S. Highway 6 , which was extended into Colorado during the 1930s . 
