U.S. Route 80 (US 80) was a U.S. highway in California that continued east across the country to Georgia. The western terminus of US 80 was in San Diego, California, and it continued east through the city on several different alignments through the years. The highway went through the Cuyamaca Mountains, encountering many switchbacks, before descending to El Centro. After passing through the sand dunes, the highway crossed the Colorado River into Yuma, Arizona.

The Old Plank Road is a plank road in Imperial County, California, that was built in 1915 as an east–west route over the Algodones Dunes. It effectively connected the extreme lower section of Southern California to Arizona and provided the last link in a commercial route between San Diego and Yuma.