Interstate 40 (I-40) is the third-longest major east–west Interstate Highway in the United States, after I-90 and I-80. Its western end is at Interstate 15 in Barstow, California; its eastern end is at a concurrency of U.S. Route 117 and North Carolina Highway 132 in Wilmington, North Carolina. Much of the western part of I-40, from Oklahoma City to Barstow, parallels or overlays the historic U.S. Route 66. I-40 intersects with eight of the 10 primary north–south interstates (all except I-5 and I-45) and also with I-24, I-30, I-44, I-77, and I-81.

I-40 enters Arizona from California at a crossing of the Colorado River at Topock in Mohave County. It heads east from Topock and begins to curve towards the north at Franconia and completes the curve to the north at Yucca. The Interstate continues to head north until it reaches Kingman. In Kingman, I-40 has a junction with US 93 at exit 48. US 93 heads towards the northwest from this junction to Hoover Dam and Las Vegas.

For the majority of its routing through Arizona, I-40 follows the historic alignment of U.S. Route 66. The lone exception is a stretch between Kingman and Ash Fork where US 66 took a more northerly, less direct route that is now State Route 66. Construction of I-40 was ongoing in the 1960s and 1970s and reached completion in 1984. With the completion of I-40 in 1984, the entire routing of US 66 had been bypassed by Interstate Highways which led to its decertification a year later in 1985.

en.wikipedia.org/wiki/Interstate_40

en.wikipedia.org/wiki/Interstate_40_in_Arizona