High Quality Content by WIKIPEDIA articles! 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.