SR 170 begins at the Interstate 15 (I-15) Riverside interchange (exit 112), approximately 60 miles (97 km) northwest of Las Vegas in Virgin Valley.

From there, the two-lane highway meanders southeasterly approximately 3 miles (4.8 km) before reaching the Riverside townsite and the Virgin River.

After another 2 miles (3.2 km), the highway turns due north, crosses the Virgin River again, and enters the city of Mesquite.

The highway travels about one more mile (1.6 km) northward through the southern portion of the city before ending at an intersection with Mesquite Boulevard (former SR 144).

[1][2][3] A gravel road approximating the alignment of present-day SR 170 appeared on official state maps by 1933.