From there, the route travels eastward, following the curvy mountainside over Rough Summit headed toward Hoover Dam.

Shortly after passing the turnoff for the Lakeview scenic viewpoint, the SR 172 designation ends 1.61 miles (2.59 km) west of the Arizona state line, just prior to a security checkpoint at the boundary with the Bureau of Reclamation's Hoover Dam Reservation.

However, it only runs a short distance in that state before looping through a new parking area at a helipad to return the way it came, the original road past that point being blocked off to prevent all but dam personnel from continuing further south.

[1] US 93 was rerouted onto the Hoover Dam Bypass when construction was completed in October 2010, and the new state highway was designated over the old route.

The entire route is in Lake Mead National Recreation Area, Clark County.