U.S. Highway 138 (US 138), commissioned in 1926, is an east–west U.S. Highway in Colorado and Nebraska that travels predominantly northeast to southwest, paralleling the South Platte River and Interstate 76 (I-76). Similarly to the spurs of the former US 66 and US 99, US 138 is an orphan route. US 38 was commissioned in 1926, but US 6 was extended over it to Long Beach, California. Therefore, US 138 still meets its former parent route's path.

Interstate 76 (I-76) is an east–west Interstate Highway in the Western United States that runs from I-70 in Arvada, Colorado – near Denver – to an interchange with I-80 near Big Springs, Nebraska. The highway measures 187.29 miles (301.41 km) long, mostly situated in Colorado but approximately three miles (4.8 km) of which is in Nebraska. Along the route, the highway runs concurrent with US Route 6 (US 6), US 85 in the Denver metropolitan area, and US 34 from Wiggins to Fort Morgan. It has no auxiliary Interstates, but it has two business routes that are located in northeastern Colorado. This route is not connected with the other I-76 that spans from Ohio to New Jersey.