U.S. Route 89 in Utah partially coincident with Interstate 15 in Utah
U.S. Route 89 (US 89) in the U.S. state of Utah is a north-south United States Highway spanning more than 502 miles (807.891 km) through the central part of the state, making it the longest road in Utah. Between Provo and Brigham City, US-89 serves as a local road, paralleling (and occasionally concurring with) Interstate 15, but the portions from Arizona north to Provo and Brigham City northeast to Wyoming serve separate corridors. The former provides access to several national parks and Arizona, and the latter connects I-15 with Logan, the state's only Metropolitan Statistical Area not on the Interstate.When US-89 was established in the state in 1926, the road initially extended north to US-91 in Spanish Fork. Following the extension of the former to the Canada–US border, Interstate 15 was constructed roughly paralleling US-89 to the west and replacing US-91 south of Brigham City. During this process, US-89 was rerouted in southern Utah and northern Arizona, with the old roadway becoming US-89A.Southern Wasatch Front
From Springville north to Salt Lake City, US-89 parallels—and for a distance overlaps—Interstate 15, following the old Arrowhead Trail, once the main highway from Salt Lake City to Los Angeles, through several downtowns. Numerous state highways connect US-89 to I-15, including SR-77 in Springville, SR-114 in Provo, SR-52 in Orem, SR-180 and SR-145 in American Fork, and SR-73 in Lehi. In Provo, US-89 meets US-189, its only branch, which heads northeast through Provo Canyon to Heber City, connecting to I-80 and bypassing Salt Lake City. North of Lehi, US-89 merges with I-15 (at exit 282), which has been built on or near the old road through a gap in the Traverse Mountains (elevation 4800 feet/1500 m) into the Salt Lake Valley. The routes split in Draper, formerly with a direct interchange north of SR-71, but US-89 traffic must now exit at SR-71 (exit 291), turn east to Factory Outlet Drive, and follow this frontage road to the location of the former split. From here to downtown Salt Lake City, US-89 is marked along State Street, a major north–south street that ends at the Utah State Capitol. After passing through Sandy, Midvale, Murray, Millcreek Township, and South Salt Lake, State Street enters Salt Lake City at the intersection with SR-201 (2100 South).
Until 2007, US-89 followed State Street to North Temple (100 North), two blocks from the capitol, but now it turns at 400 South, following the former alignment of SR-186 and SR-176 west and north on 300 West, and rejoining its pre-2007 route at North Temple. In this area, modern US-89 runs for one block with the UTA TRAX Red Line in its median before crossing the TRAX line in Main Street's median, then passing the Frank E. Moss United States Courthouse, Pioneer Park, the historic Warehouse District at Pierpont Avenue, Japantown, Vivint Arena, the Arena TRAX station, the Triad Center, and West High School. As it leaves downtown, 300 West curves northwesterly and becomes Beck Street, meeting the modern terminus of SR-186 at Victory Road at the back side of Capitol Hill.Northern Wasatch Front
US-89 leaves Salt Lake City at exit 312 of I-15, where it acts as I-15's frontage roads. Just south of I-15's junction with I-215, US-89 splits to the northeast, passing through Bountiful and Woods Cross. A northerly curve onto 500 West removes the highway from Bountiful's Main Street, and it merges with I-15 at exit 317 to bypass Centerville and Farmington, where the old road (former US-91, but never US-89) is SR-106, through the narrow strip of land that separates Farmington Bay from the Wasatch Mountains. US-89 leaves I-15 at exit 324, where the Legacy Parkway also ends, and proceeds north on a freeway. This portion of US-89 is the only one to include exit numbers based on its mileage, as opposed to the overlapping I-15 or I-70. The freeway ends after US-89 crosses SR-273, the former surface alignment of US-91 in both directions, and heads north as a four-lane road along the Wasatch foothills, to the east of Layton and Hill Air Force Base. This portion is planned to be upgraded to freeway status by 2023.  After crossing I-84 in Uintah, US-89 enters Ogden, which it traverses via Washington Boulevard, rejoining old US-91 (now SR-26) south of downtown. Beyond Ogden, US-89 continues in a general northerly direction along the thin strip between Willard Bay and the Wasatch Mountains to Brigham City, where it finally turns east away from the I-15 corridor.
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