U.S. Route 138, is a short (72 miles) east-west freeway in Colorado & Nebraska that runs predominantly northeast toward southwest paralleling the South Platte River & Interstate 76.The western end is in Sterling, Colorado, where it met U.S. Route 38 from 1926 to 1931 (US 38 became U.S. Route 6); the eastern end is at U.S. Route 30 north of Big Springs, Nebraska.