Interstate 40 in California
Designed to be part of the original Interstate System in 1947, I-40 was commissioned from California to North Carolina in 1955. One of the later chargeable Interstates to be added to the system, it was completed in the 1980s when a final section in North Carolina opened. It replaced a multitude of US Highways, including the infamous US 66 from Oklahoma City, OK to Barstow, CA.
Completed in sections between the 1950's and 1970's, I-40 runs through the southern-most portion of the Mojave Desert in California. The highway enters near Needles at the Colorado River, along a widened bridge built for US 66, and runs directly west from there. There are very few towns along this stretch of I-40, as well as exits: there are less then 25 exits in California, most of them for local access only in case of emergency with no services even though it stretches 250 miles across the state. The uninterrupted drive through the desert is arguably one of the most stunning in the system - from rolling hills to flat terrain, with Joshua Trees dotting the horizon. California's segment of I-40 is located entirely in San Bernardino County.
At first, I-40 was routed along the Old National Trails Highway with US 66 before freeways upgrades. At first, only a small stub freeway was built through Barstow, built primarily due to the freeway upgrades done to US 91/I-15, in 1960. The last part completed within the state ran from modern Goffs/Essex to Ludlow, bypassing the two lane segment of US 66 between the same points. The new route had all the characteristics of the modern Interstate: four lanes, controlled access, and a nearly straight-as-an-arrow path. This left many old towns along US 66 to wither away as it's path dipped slightly south into the Sonoran Desert.
Due to lack of urban and suburban development in the area, I-40 remains largely untouched from when it was opened. Upgrades are being made to bridges, and the road is being widened from the I-15 junction through Barstow. Even though it was replaced with I-40, US 66 is still well signed in these parts by California and the County of San Bernardino. The old road is now County Road 66, and Historic Route 66 is well signed along the Interstate at almost every exit.