Interstate 15 is the main north-south freight route of the Mountain West, running 1,433 miles from San Diego, California to Sweet Grass, Montana on the Canadian border. It is the longest north-south interstate west of the Rockies and the designated US segment of the CANAMEX trade corridor connecting Mexico and Canada through the western interior. The route ties Southern California's logistics hubs to Las Vegas, Salt Lake City, and the agricultural and energy economies of Idaho and Montana.
The geography is dramatic. From the San Diego coast, I-15 climbs through the Cajon Pass (4,190 ft), the gateway between the LA Basin and the Mojave Desert, then descends to Las Vegas, climbs again across the Virgin River Gorge in Arizona's narrow corner, and continues over high desert to Salt Lake City. North of Salt Lake it threads the Wasatch Front, climbs Monida Pass (6,870 ft) on the Idaho-Montana border, and rolls across high Montana plains to the international crossing at Sweet Grass.
I-15 is one of the highest-volume freight corridors in the West, especially the segment between Barstow and Las Vegas, which carries a continuous stream of containers and produce trucks. Holiday weekends produce notorious traffic jams between Las Vegas and the LA Basin, backups of 20+ miles are routine on Sunday evenings. Winter chain controls are common in the Cajon, Virgin River Gorge, and Monida Pass segments.
- Longest north-south interstate west of the Rocky Mountains
- Designated CANAMEX trade corridor between Mexico and Canada
- Crosses six states: CA, NV, AZ (29 miles only), UT, ID, MT
- Cajon Pass (4,190 ft) is the primary truck route between LA and the Mojave
- Virgin River Gorge in AZ is one of the most expensive interstate sections ever built (per mile)
- Monida Pass (6,870 ft) on the ID/MT border is closed regularly in winter
- Carries the bulk of LA→Las Vegas freight and weekend recreational traffic