When it opened, the Virgin River Gorge passage was the most expensive section of rural Interstate per mile.

I-15 crosses the river for the first time just beyond Littlefield, and soon passes another interchange serving local roads eastward.

[7] The canyon opens up slightly at the Cedar Pocket interchange (exit 18), allowing for a rest area.

[8] At mile 22.5, the highway crosses the Virgin River for the final time, continuing east along the smaller Black Rock Gulch before then turning slightly northeast into a flatter area.

[7] The Old Spanish Trail from Southern California had two routes through northwestern Arizona, splitting at Littlefield; one went north toward central Utah, and the other went northeast through the Virgin River Gorge, straddling the state line to the Four Corners area.

[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.

[15] To help quicken construction, the state of Utah loaned a portion of their federal highway funds to Arizona.

Flash flooding and quicksand in the gorge repeatedly caused problems, with equipment and materials apparently disappearing overnight.

Worse, the project was to claim a life, when in October 1969, a helicopter performing reconnaissance on the gorge crashed due to wind, killing the pilot.

To help navigate the gorge's rugged and unforgiving terrain, a special piece of equipment, called a swamp buggy, had to be brought from Texas.