The main branch passes over the Colorado River just south of the dam and Lake Powell and then enters Utah.

The US 89A branch turns westward and crosses the Colorado River via the Navajo Bridge at Marble Canyon near Lees Ferry.

It then climbs on to the Kaibab Plateau, connecting with Arizona State Route 67 at Jacob Lake which provides access to the North Rim of the Grand Canyon.

Just before entering Utah, a junction with Arizona State Route 389 in Fredonia serves the Pipe Spring National Monument.

Historically, the route extended south to Nogales and served numerous sites of the National Park System in Arizona.

From Ogden the highway runs north until it meets US 91 at Brigham City, where it turns east to serve Cache Valley and Logan, concurrent with US 91.

In Logan, US 89 forms the southern portion of Main Street before splitting off to the east, passing by the campus of the Utah State University.

Passing northward along the western border of Wyoming with Idaho, US 89 enters the Grand Teton National Park.

[5] The Kings Hill Scenic Byway passes through the Little Belt Mountains in the Lewis and Clark National Forest in Montana.

The route travels over the Kings Hill Pass which snow removal crews work to keep open throughout the winter season.

In central Arizona, the need for a north–south U.S. Highway was largely superseded by the completion of I-17, which now carries the bulk of the traffic and all of the heavy trucks along this north–south corridor.

US 89 in central Utah was discontinuous for most of 1983 due to a landslide that destroyed the town of Thistle and closed the highway for about eight months.

[citation needed] From early 2013 to mid 2015, US 89 was closed approximately 25 miles (40 km) south of Page, due to a geological event that caused the roadway to buckle and subside.

[10] US 89T opened on August 29, 2013, a 28-mile (45 km) paved portion of a Navajo route to serve as a long-term bypass of the closed section.