Currently, the commissioned route extends from Piegan, Montana to Flagstaff, Arizona. Yellowstone National Park bisects the highway into two sections as roads within America's oldest national park are unsigned and implied.
The signed portion of US 89 in Montana is 404 miles in length from the Canadian border to the northern boundary of Yellowstone via St. Mary's, Choteau, Great Falls, Whte Sulphur Springs, and Livingston. The road mirrors the Glacier-Yellowstone portion of the National Park to Park Highway from Browning to Gardiner which connected 12 western national parks a century ago.
The 163 mile signed portion of US 89 in Wyoming starts at the south boundary of Yellowstone National Park (where it is known as the John D. Rockerfeller Jr. Parkway) and ends at the Idaho stateline passing through Jackson, Alpine, and Afton en route. The unsigned portion of the route within Yellowstone follows the Great Loop Road from West Thumb to Mammoth Hot Springs via Old Faithful, Madison, and Norris. The Rockerfeller Parkway connects Yellowstone with Grand Teton.
The Idaho portion of US 89 is 45 miles in length from the 111th meridian in the east to the 42nd parallel in the south via Montpelier.
The 502 mile Utah portion of US 89 extends from the Idaho state line in the north to the Arizona state line in the south via Brigham City, Logan, Salt Lake City, Provo, and Richfield.
The 138 mile Arizona portion of US 89 commences at the 37th parallel and concludes at I-40 via Page.
The 92 mile original route between Kanab, Utah and Bitter Springs, Arizona via Fredonia and Jacob Lake was resigned as US 89A in 1960.