 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. 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. By 1965, the overpass over Black Rock Road (northwards) was finally complete.
