Interstate 15

From Academic Kids

Interstate 15, or I-15, is a north-south interstate highway in the western United States, traveling through the states of Montana, Idaho, Utah, Arizona, Nevada, and California. In California, this freeway is a major transportation corridor linking the San Diego Metropolitan area with the east side of the Los Angeles Metropolitan area, and various inter- and suburban communities between these metropolitan areas. It also serves as the primary access route from Southern California to Las Vegas, Nevada, a major travel/tourist destination througout the year. More recently, due to rapid population growth and associated residential, commercial, and industrial development in the Mojave Desert communities of Victorville, Hesperia, Apple Valley, and Adelanto (all in California), this interstate highway has begun to serve as a heavily traveled commuter route.


Route Summary

This highway's south terminus is in San Diego, California at the junction with Interstate 8 (I-8). South of I-8 it does not have "Interstate" status per Federal Highway guidelines for such roads. Instead, it is classified as a state route and is numbered as California State Route 15 (CA/SR-15) from the I-8 interchange to the Interstate 5 (I-5) interchange at San Diego's Barrio Logan. It is planned by CalTrans that "Interstate" status will be assigned to this segment once necessary upgrades are completed. The northern terminus is at Sweetgrass, Montana at the international border between the United States and Canada.

North of its junction with the Riverside Freeway, California State Route 91 (CA/SR-91), in the Inland Empire near Corona, the route follows (roughly) the old US Route 91. North of Devore, California the highway follows the approximate alignment of historic US Route 66 until about the Mojave River 35 miles (56 km) to the north.

Interestingly, the south terminus of Interstate 15 was originally planned to be in San Bernardino at an interchange with the San Bernardino Freeway, Interstate 10 (I-10). This was logical as I-15 was following the old alignment of the historic route U.S. Route 66 which passed through San Bernardino. The segment was completed accordingly. However, legislation was later passed to extend the interstate to San Diego. But instead of extending the existing freeway from the I-10 interchange south, CalTrans created a new segment in Devore, California that 'branched' off of the original alignment and bypassed San Bernardino altogether. This segment's alignment is generally northeast to southwest for about 15 miles (24 km). Then, in Fontana/Rancho Cucamonga, California, its directional alignment shifts to north-south where it eventually junctions with Interstate 10 (about 15 miles west of the original interchange in San Bernardino). The segment that had been built from Devore to San Bernardino was retained as an interstate, but was re-numbered as Interstate 215 (California) or I-215. Note that during the construction of I-15's present alignment, and for some time afterwards, I-215 was numbered as I-15E. Review the Interstate 215 (California) page for further discussion regarding its unusual history and alignment.

Note there are three bypasses and loops identified as Interstate 215: in the Inland Empire region of California; in Las Vegas, Nevada; and in Salt Lake City, Utah.

In California, I-15 has, at least, five different names throughout its length. Between I-8 (Mission Valley Freeway) to the Riverside/San Diego county line, it is named the Escondido Freeway. (The portion of the Escondido Freeway passing through the Marine Corps Air Station at Miramar is also known as the Semper Fi Freeway.) Between the county line and California State Route 74 CA/SR-74 (the Ortega Highway) in Lake Elsinore, it is named the Temecula Valley Freeway. From CA/SR-74 to Limonite Avenue in Riverside County, it is known as the Corona Freeway. From Limonite Avenue to the northern junction with Interstate 215 (California) or I-215 spur in Devore, it is named the Ontario Freeway. From the northern I-215 junction to Interstate 40 (I-40) junction in Barstow, California, it is named the Barstow Freeway. Finally, from Barstow to the California/Nevada state line it is named the Mojave Freeway. Detailed information about freeway intersections and communities along these routes can be found at their individual entries.

Missing image
Northbound, I-15 makes a steep descent from Mountain Pass into the Ivanpah Valley. In the middle distance, the casinos of Primm straddle the freeway right at the Nevada border, while those of Jean are further off, to the left; Las Vegas is immediately on the far side of the hills on the horizon.


292 473 California
124 201 Nevada
29.40 47.63 Arizona
401 650 Utah
196 318 Idaho
396 642 Montana
1,438.40 2,330.21 Total

Major cities along the route

Major intersecting freeways and highways

Listed in order from south to north:




Interstate 15 does not intersect any major roads in Arizona.




Spur routes



  • Managed Lanes Project- Initated during fall 2003 and will finished late 2007. Portion of CA-56 to Centre City Pkwy (former US 395). More info in "reference" section; See also high occupancy toll.
  • At the time it was built, the section running through the northwest corner of Arizona (the Virgin River gorge) was the most expensive section (per mile) of the entire interstate system.
  • The sign for the Zzyzx exit, the alphabetically last place name in the United States, is a well-known landmark along the drive from Los Angeles to Las Vegas on I-15.
  • Interstate 15 had an eastern branch bypassing San Bernardino, California, and a western branch in Idaho. I-215 around San Bernardino was I-15E, and the western I-86 was once called I-15W.
  • The eastern section of I-215 in Salt Lake City, from the south interchange with I-15 east to I-80, was once known as I-415.
  • I-15 ends at the border between Montana and Alberta, where it becomes AB Provincial Highway 4. This route can be used to go into the cities of Calgary and Edmonton.



Template:Ed divPrimary Interstate Highways Missing image
Interstate Highway marker

4 5 8 10 12 15 16 17
19 20 22 24 25 26 27 29
30 35 37 39 40 43 44 45
49 55 57 59 64 65 66 68
69 70 71 72 73 74 75 76 (W)
76 (E) 77 78 79 80 81 82 83
84 (W) 84 (E) 85 86 (W) 86 (E) 87 88 (W) 88 (E)
89 90 91 93 94 95 96 97
99 238 H-1 H-2 H-3
Unsigned Interstate Highways
A-1 A-2 A-3 A-4 PRI-1 PRI-2 PRI-3
Two-digit Interstates - Three-digit Interstates
Gaps in Interstates - Intrastate Interstates
Interstate standards - Proposed Interstates

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