Interstate 15
Route information
Maintained by Arizona Department of Transportation
Length	29.43 mi [1] (47.36 km)
Existed	1962 [2]–present
NHS	Entire route
Major junctions
South end	I-15 towards Las Vegas, NV
North end	I-15 towards St. George, UT
Location
Country	United States
State	Arizona
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future Arizona State Highway System Interstate US State Proposed Former
← I-10 → I-17

Interstate 15 (I-15), a transcontinental Interstate Highway from San Diego, California to the Canadian border, passes through Mohave County in the far northwest corner of the U.S. state of Arizona. Despite its length of 29.43 miles (47.36 km) and isolation from the rest of the state in the remote Arizona Strip, it is notable for the scenic section through the Virgin River Gorge. The highway heads in a northeasterly direction from the Nevada border northeast of Mesquite, Nevada to the Utah border southwest of St. George, Utah.

The southern portion of the routing of I-15 was built close to the alignment of the old U.S. Route 91 (US 91), but the northern section through the Virgin River Gorge was built along an alignment that had not had a road previously. The southern section of the highway was complete and opened in the early 1960s, while the section through the gorge did not open to traffic until 1973. When it opened, the portion of I-15 through the Virgin River Gorge was the most expensive section of rural Interstate per mile.

Route description

The highway is signed and designated the Veterans Memorial Highway, ^[3] a designation which continues into Utah. ^[4] I-15 parallels the Virgin River for its entire length in Arizona, but the terrain abruptly becomes more rugged at mile 13, where the Virgin River Gorge begins. ^[5] Traffic volumes along I-15 are approximately 23,000 vehicles per day. ^[6] The highway is also a part of the CANAMEX Corridor, a trade corridor in North America linking Edmonton in Canada and Mexico City. ^[7]

The highway enters the state in Mohave County northeast of Mesquite and Las Vegas, Nevada, paralleling the old US 91 heading northeast on an alignment north of the river. The first interchange is exit 8 at Littlefield, where old US 91 turns north to avoid the gorge. I-15 crosses the river for the first time just beyond Littlefield, and passes another interchange serving local roads east of Littlefield. This exit, exit 9, is a right-in/right-out design with frontage roads, and was constructed after the initial opening of I-15. Access under I-15 is provided just south of the ramps. ^[5]

Beyond exit 9, I-15 enters the Virgin River Gorge, first passing through the section known as "The Narrows". The gorge features limestone cliffs that are as high as 500 feet (150 m) above the highway. There are several pulloffs along the highway that allow access to the cliffs of the gorge. ^[8] Within the canyon, through which it ascends northbound and descends southbound, five bridges cross or travel above the river. ^[9] The highway generally follows the winding course of the river, but several rock cuts allow it to bypass bends. ^[5]

The canyon opens up slightly at the Cedar Pocket interchange (exit 18), allowing for a rest area. This rest area was turned over to the federal Bureau of Land Management in 2002 which maintains the nearby Virgin River Gorge Recreation Area. ^[10] I-15 continues to parallel the Virgin River, but deviates more than through the narrower part of the canyon. ^[5] Foliage through the canyon consists of tamarix, ash, cottonwoods, willows and Joshua trees. Wildflowers such as globemallow, marigold, and sand verbena are in bloom during the spring along the highway's path through the gorge. ^[8] At mile 22.5, the highway crosses the Virgin River for the final time, continuing east along the smaller Black Rock Gulch before turning slightly northeast into a flatter area. The final interchange (exit 27) provides local access, and a weigh station/ port of entry formerly served both sides of the road near mile 28 before the Utah state line. ^[5] The port of entry and weigh station are now combined into a joint Arizona/Utah facility just north of the state line that is jointly staffed by personnel from the Arizona Department of Transportation (DOT) Motor Vehicle Division and Utah DOT Motor Carrier Division. I-15 continues on into Utah providing access to St. George as well as Salt Lake City. ^[5]

History

The Old Spanish Trail to Southern California had two routes through northwestern Arizona, splitting at Littlefield; one went north towards central Utah, and the other went northeast through the Virgin River Gorge, straddling the state line to the Four Corners area. ^[11] When the Arrowhead Trail was marked in the 1920s, and U.S. Route 91 in 1926, automobile travelers between Nevada and Utah followed the northerly routing, turning east in Utah to reach St. George. ^[12]

When the Interstates were planned, federal authorities decided to save 12 miles (19 km) over US 91 and pass through the Virgin River Gorge to take advantage of its scenery and lower grades for trucks. ^{[13] [14]} Construction was completed first, in the early 1960s, on the portion between Nevada and the gorge. The bridges over Big Bend Wash were completed in 1962. The bridge over the Virgin River near Littlefield was completed by 1964. North of the gorge, the overpass over Black Rock Road was completed in 1965. ^[9]

Construction through the gorge was slower and much more difficult and that segment would not fully open until December 14, 1973. ^[15] To help expedite the construction of the segment through the gorge, the state of Utah forwarded a portion of their federal highway funds to Arizona. ^[14] The highway is of little importance to the transportation needs of Arizona since it does not link any Arizona communities, but it does serve as a vital link between the state capital of Utah in Salt Lake City and Las Vegas and Los Angeles to the southwest. ^[16] Arizona would eventually repay the funds they received from Utah. ^[14] Flash flooding and quicksand in the gorge caused problems throughout the project with equipment and materials seeming to disappear overnight as a result. In October 1969, a helicopter performing reconnaissance in the gorge brushed against the cliffs and crashed due to high winds, killing the pilot. To help navigate the rugged terrain in the gorge, a special piece of equipment called a swamp buggy had to be brought in from Texas. ^[17] The planned routing through the gorge required the construction of four bridges over Virgin River. The westernmost bridge and the bridge carrying the northbound lanes at the third bridge location from the west were completed in 1972. By 1973, all five bridges were complete through the gorge. ^[9] Even before its opening, it was promoted as the most scenic highway in the state; a 1988 article in Arizona Highways said that the project "enhanced rather than distracted from Nature's handiwork". The Virgin River was rechanneled 12 times in what was, at the time, the most expensive rural freeway in the country, costing about $10 million per mile ($49 million in 2007). ^{[13] [18]}

Exit list

The entire route is in Mohave County.

References

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