Interstate 15

Interstate 15

Infobox road

length_ref=cite web|publisher=Interstate Guide|url=|title=Interstate 15 @|accessdate=2008-02-15]
terminus_b=Jct|state=AB|Hwy|4 at Canadian border near Sweetgrass, MT

Interstate 15 (I-15) is the fourth-longest north-south transcontinental interstate highway in the United States, traveling through the states of California, Nevada, Arizona, Utah, Idaho, and Montana. The Utah and Arizona portions have been officially designated the 'Veterans Memorial Highway'.cite web
url =
title = Utah@Rocky Mountain Roads - Interstate 15
accessdate = 01-02-2008
publisher = Aaroads

Since I-15's inception, it has served as a long-haul route for North American commerce. It is now officially chartered for this purpose. From the junction of Interstate 515 in Las Vegas to the Canadian border I-15 forms part of the CANAMEX Corridor, a High Priority Corridor, as a result of the North American Free Trade Agreement.cite web
url =
title = CANAMEX CORRIDOR, The safe, smart and secure corridor
accessdate =01.02.2008
publisher = Canamex Corridor Project

Local portions were built to connect the Inland Empire with San Diego in California, facilitate tourism access to Las Vegas, interconnect all of the Metropolitan Statistical Areas in Utah except Logan, and provide freeway bypasses for Pocatello, Idaho Falls and Great Falls.

Since I-15's initial construction, California, Nevada, and Utah have consistently ranked in the fastest growing areas of the United States. As a result, the I-15 corridor has substantially increased in population and commuter traffic has increased the traffic burden on the freeway. Current population estimates are that more than 75 percent of Utah's populationcite web
url =
title = Population-Visitor Center-
accessdate = 01-02-2008
publisher = Utah Travel Industry
] , 19 percent of California's population, and more than 70 percent of Nevada's populationcite web
url =
title = 2006 Estimates by County
accessdate = 01-02-2008
publisher = Nevada Small Business Development Center
] live in counties where Interstate 15 is the primary transportation corridor. Similarly, in California, I-15 is seeing more commuter traffic due to the growth of the Mojave Desert communities of Victorville and Barstow, California. In all of these states, I-15 has recently been or is currently in the process of being upgraded to increase capacity.cite web
url =,V:69,
title = Utah Department of Transportation, Projects Under Construction
accessdate = 01-02-2008
publisher = Utah Department of Transportation
] [cite web
url =
title = District 1 Construction Report
accessdate = 01-02-2008
publisher = Nevada Department of Transportation
] [cite web
url =
title = Interstate 15 Major Improvements
publisher = California Department of Transportation
] The Arizona, Idaho and Montana portions have retained their rural, long-haul character. Although Arizona has also grown substantially since I-15's inception, I-15 only serves an isolated corner of the state.

Due to this rapid area growth, the I-15 corridor is the focus of several mass transit projects. The Las Vegas Monorail, FrontRunner commuter rail system and TRAX light rail in Salt Lake City are mass transit lines loosely parallel to I-15 that are now in operation. Between Los Angeles and Las Vegas has long been proposed as a maglev train route; in 2004 the California-Nevada Interstate Maglev project held public meetings on the plan. [cite web
author = Staff.
url =
title = FRA to begin environmental study for California-to-Nevada Maglev project
accessdate = 04.21.2007.

Route description


This highway's southern terminus is in San Diego, California at Interstate 8, 18 miles (29 km) north of the international border with Mexico. However, work is being done to extend this to Interstate 5. The current work on this extension is signed State Route 15. There is a continuous freeway between I-8 and I-5, but various intersections and acceleration/deceleration lanes are not up to interstate standards. The northern terminus is in Sweetgrass, Montana at the international border between the United States and Canada, where it becomes Alberta Highway 4.


North of its junction with the Riverside Freeway, State Route 91, in the Inland Empire near Corona, the route roughly follows the former routes of U.S. Highway 91 and U.S. Highway 395. North of Devore, the highway follows the approximate alignment of historic U.S. Highway 66 along with U.S. 91 and 395. U.S. 395 breaks away at Hesperia and the route continues the approximate route of co-signed 66 and 91 until about the Mojave River, 35 miles (56 km) to the north. At that point, I-15 follows the old route of U.S. 91 exclusively. For many parts of the highway, high-voltage power lines, like Path 46 and Path 27, almost all from the Hoover Dam, follow the freeway. Many of these link distant power stations to the Los Angeles metropolitan area.

The starting point of Interstate 15 was originally planned to be in San Bernardino at an interchange with the San Bernardino Freeway, I-10. This was logical as I-15 was following the old alignment of the historic 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, the California Department of Transportation made a new segment in Devore 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, its directional alignment shifts to north-south where it eventually junctions with Interstate 10 (about 15 miles or 24 kilometers 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. Note that during the construction of I-15's present alignment, and for some time afterwards, I-215 was numbered as I-15E, and its actual mileage would begin at Interstate 10.


Interstate 15 begins in Primm, continues through Las Vegas along the Las Vegas Strip corridor. Then the interstate crosses the border with Arizona in Mesquite. The whole interstate in Nevada runs entirely in Clark County, for a distance of convert|123.77|mi|km.


I-15 just clips the northwestern corner of Arizona with a total length of 29.4 miles (47 km). [Arizona Department of Transportation Project 015 MO 000 H577901C, sheet 73 of 103 - revised May 2005] The stretch is separated from the rest of the state and has one major exit, at Beaver Dam/Littlefield, Arizona. It includes a spectacular section where the road twists between the narrow walls of the Virgin River Gorge.


I-15 continues through Utah for just over 400 miles (640 km). It is the main north-south connection for the state. The highway approximately follows the old alignment of U.S. Highway 91 from St. George to Brigham City. The highway passes through the fast-growing Dixie region, which includes St. George, Cedar City, and eventually most of the major cities and suburbs along the Wasatch Front, including Provo, Orem, Sandy, West Jordan, Salt Lake City, Layton, and Ogden. Near Cove Fort, Interstate 70 begins its journey eastward across the country. The interstate merges with I-80 for about 3 miles (5 km) from South Salt Lake to just west of Downtown Salt Lake City and also merges with Interstate 84 from Ogden to Tremonton. Along nearly its entire length through the state, I-15 winds its way along the western edge of a nearly continuous range of mountains (the Wasatch Range in the northern half of the state). The only exceptions are when it passes through the mountains south of Cedar City and again north of Cove Fort.


I-15 passes through Idaho for nearly 200 miles (320 km). The highway runs through Pocatello, Blackfoot, and Idaho Falls.


Interstate 15 continues onward through nearly 400 miles (640 km) of Montana through the cities of Butte, Helena and Great Falls, intersecting with Interstate 90, Interstate 115 and Interstate 315. At Sweetgrass, I-15 terminates upon crossing the international border into Alberta, Canada; however, I-15 signage is present on Alberta Highway 4 southbound from Lethbridge to the U.S.-Canada Border.


Interstate 15 was constructed along the route of U.S. Route 91. Once Interstate 15 was relatively intact U.S. 91 was decommissioned, except for one part in Northern Utah/Southern Idaho where Interstate 15 instead followed the route of former U.S. Route 191.

Interstate 15 had an eastern branch bypassing San Bernardino, California, and a western branch in Idaho. I-215 around San Bernardino was I-15E [ entry for Interstate 215 California] , and the western I-86 was once called I-15W. [ entry for I-86 Western]


Redesignation of SR 15 in San Diego as I-15 will eventually occur when the freeway's interchange with SR 94 is updated to Interstate standards. The interchange currently has left-exits and blind merges, and is due to be updated with a long-awaited widening of SR 94 in 2008. At that time SR 15 will be resigned as part of I-15.

Major intersections

Listed in order from south to north:


*Interstate 8 in San Diego
*Interstate 215 in Murrieta
*Interstate 10 in Ontario
*Interstate 215 in Devore
*Interstate 40 in Barstow


*Las Vegas Beltway ("I-215" to the east, "CC 215" to the west) in unincorporated Clark County (Paradise) near McCarran International Airport
*U.S. Route 95 (also U.S. Route 93 and Interstate 515 to the east) in Las Vegas


Interstate 15 does not intersect any interstate highway in Arizona.


*Interstate 70 in Cove Fort
*Interstate 215 in Murray
*Interstate 80 in South Salt Lake; they merge for about 3 mi (5 km) into Salt Lake City
*Interstate 215 in North Salt Lake
*Interstate 84 in Ogden; they stay merged until Tremonton


*Interstate 86 in Pocatello


*Interstate 90 in Butte; they are merged for 9 miles (14.5 km)
*Interstate 115 in Butte.

Auxiliary routes

*Inland Empire, California - I-215
*Spur to Henderson, Nevada outside Las Vegas - I-515
*Beltway Las Vegas, Nevada - I-215
*Salt Lake City, Utah - I-215
*Butte, Montana - I-115
*Great Falls, Montana - I-315

ee also

*State Route 15
*U.S. Route 66
*U.S. Route 91


External links

*2005 Rand McNally "The Road Atlas 2005" - newest feature- interstate mileage by state


* [ California Highways: SR 15]
* [ Cal-NExUS: Route 15 North]
* [ Cal-NExUS: Route 15 South]


* [ I-15 Completed December 14, 1973]

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Interstate 77 — Route information Length …   Wikipedia

  • Interstate 69 — Route information Length …   Wikipedia

  • Interstate 10 — Basisdaten Länge: 2460 mi/3960 km Bundesstaaten: Kalifornien Arizona New Mexico Texas …   Deutsch Wikipedia

  • Interstate 80 — Route information Length …   Wikipedia

  • Interstate 91 — Route information Length …   Wikipedia

  • Interstate 5 — Basisdaten Länge: 1381 mi / 2222 km Bundesstaaten: Kalifornien Oregon Washington …   Deutsch Wikipedia

  • Interstate 93 — Route information Length …   Wikipedia

  • Interstate 71 — Route information Maintained by …   Wikipedia

  • Interstate 87 — Map of the northeastern United States with I 87 highlighted in red Route information …   Wikipedia

  • Interstate 20 — Basisdaten Länge: 1535 mi/2470 km Bundesstaaten: Texas Louisiana Mississippi Alabama …   Deutsch Wikipedia

  • Interstate 77 — Basisdaten Länge: 611 mi/984 km Bundesstaaten: South Carolina North Carolina Virginia …   Deutsch Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.