Planning on how to route the freeway over the Rocky Mountains began in the early 1960s. The US 6 corridor crosses two passes: Loveland Pass, at an elevation of and Vail Pass, at . Engineers recommended tunneling under Loveland Pass to bypass the steep grades and hairpin curves required to navigate US 6. The project was originally called the Straight Creek Tunnel, after the waterway that runs along the western approach. The tunnel was later renamed the Eisenhower-Johnson Memorial Tunnel, after U.S. President Dwight D. Eisenhower and Colorado Governor Edwin C. Johnson.