U.S. Route 91
|Length:||172.663 mi (277.874 km)|
|Existed:||1926 – present|
|South end:||I-15 / I-84 in Brigham City, UT|
| US-89 in Logan, UT
US-30 in McCammon, ID
I-86 in Pocatello, ID
|North end:||I-15 Bus. / US-26 in Idaho Falls, ID|
U.S. Route 91 is a north–south United States highway. The highway currently serves as a connection between the Cache Valley area of Utah and Idaho to the Salt Lake and Idaho Falls population centers. Prior the mid-1970s, U.S. 91 was an international commerce route from Long Beach, California to the Canadian border north of Sweetgrass, Montana. The highway served as the main street of most of the communities it served, including Las Vegas Boulevard in Las Vegas and State Street in Salt Lake City. From Los Angeles to Salt Lake City, the route was largely built along the corridor of the Arrowhead Trail. The route has been largely replaced by Interstate 15. A portion of the highway's former route in California is currently State Route 91.
Route description 
US-91 begins at Brigham City and winds its way through the Wellsville Mountains using Box Elder and Wellsville Canyons for its path to the Cache Valley. Along the way it passes Mantua and Lake Mantua and passes over Sardine Summit. Once entering Cache Valley it serves as the major thoroughfare of the valley. Logan is the largest city in the valley. Both the Utah and Idaho portions of Cache Valley are part of the Logan Utah Metropolitan Statistical Area.
The Utah section of US-91 is defined at Utah Code Annotated § 72-4-115(1).
U.S. 91 continues serving the Idaho portion of the Cache Valley with Preston as the largest city. The highway passes by the Bear River Massacre Site, a National Historic Landmark, near Preston, and over the geologically significant Red Rock Pass, near Downey. The U.S. 91 corridor in Idaho's Cache Valley was the primary filming location for the 2004 movie Napoleon Dynamite.
After leaving Cache Valley, the highway then crosses back to rejoin Interstate 15. At Pocatello, U.S. 91, U.S. 30, and I-15 Business Loop separate from Interstate 15 and run concurrently, passing through a small portion of the Idaho State University campus. U.S. 30 separates from U.S. 91 near Pocatello's city hall at what was once the starting point of one of Idaho's first designated highways, the Yellowstone Park Highway. From this point the highway generally follows the original route of the Yellowstone Park Highway northeastward, until it reaches its terminus at its intersection with U.S. 26, south of Idaho Falls.
At its peak, from 1947 to 1965, U.S. 91 extended from the Pacific Ocean at Long Beach, California to Coutts, Alberta. North of Riverside, California, U.S. 91 mostly paralleled modern I-15. There are some parts where U.S. 91/I-15 had divergent paths. The more southerly is from Littlefield, Arizona to Saint George, Utah where the two routes took different paths through the Arizona Strip. The more northerly and longer is the surviving portion of U.S. 91 from Brigham City to Downey, where Interstate 15 follows an old route of U.S. Route 191.
Utah first submitted a petition to AASHTO to have the U.S. 91 designation truncated in 1971. This petition was approved on June 21, 1971. However, the state did not take action until 1974. Utah officials co-ordinated a second petition with the transportation departments of California, Nevada and Arizona. In this unified petition officials in Utah proposed the number changeover take place in 1974. Nevada requested postponing the deletion of U.S. 91 as Nevada expected to complete the last piece of I-15 in 1975. Nevada officials suggested U.S. Route 40 be similarly truncated, as this highway largely duplicated Interstate 80 in the same states. Despite Nevada's request, the petition was submitted and approved in 1974.
Retracing the path of historic U.S. Route 91 is possible but difficult. In most cities the route of U.S. 91 is still in use as a local street or highway. In many rural areas, I-15 was literally built on top of the former U.S. 91.
The highway passed through the following states:
- California (until 1974)
- Nevada (until 1974)
- Arizona (10 miles (16 km) in the Arizona Strip, until 1974)
- Montana (until 1980)
U.S. 91's original southern terminus was at the intersection of Atlantic Avenue (historically SR 15) and East Pacific Coast Highway (SR 1) in Long Beach. This intersection also marked the historic western terminus of US 6, which proceeded west from that intersection. East of the intersection, U.S. 91 proceeded east along East Pacific Coast Highway to Los Alamitos Circle.
The portions in California were replaced with:
- State Route 1 (Pacific Coast Highway from Atlantic Avenue to the Traffic Circle)
- State Route 19 (Lakewood Boulevard from the Traffic Circle to Lincoln Avenue)
- State Route 214 (route no longer a state highway — Carson Street and Lincoln Avenue)
- State Route 91
- Interstate 215
- Interstate 15
The route of U.S. 91 in Nevada was replaced with I-15 in 1974.
In Las Vegas, U.S. 91 was better known as Las Vegas Boulevard (State Route 604 after the 1976 renumbering of most Nevada state highways). The intersection of Las Vegas Boulevard and Fremont Street is the historic intersection with U.S. 93 and U.S. 95. Here, U.S. 466 parted ways with U.S. 91 and headed southeast on Fremont Street with southbound U.S. 93 and 95. At this intersection, U.S. 93 and 95 departed Fremont Street and turned northeast onto Las Vegas Boulevard, heading northbound with U.S. 91. A few blocks further up, at Bonanza Road, U.S. 95 turned west until it hit Rancho Drive, then continued north. U.S. 91/93 stayed aligned with Las Vegas Boulevard, which turned into Salt Lake Highway after departing the city of North Las Vegas.
Until its decertification in 1974, U.S. 91 followed I-15 to exit 112, where it took present-day NV 170 through Riverside to Mesquite, turned right onto NV 144 (Mesquite Boulevard and Sandhill Boulevard), and then followed Hillside Drive into Arizona (where the road became Fairview Avenue).
U.S. 91 entered Arizona from Nevada on Fairview Avenue and followed it northeast to Littlefield. Once Fairview Avenue crosses I-15, it became Cane Beds Road through downtown Beaver Dam and into Utah, where the road continued as Old Highway 91.
From the State Line to Saint George US-91 followed a semi-circular route that is now simply called Old Highway 91. Old Highway 91 continues to Santa Clara and what is now SR-18 to St. George. Where SR-18 intersects St. George Blvd, U.S. 91 then continued east on St. George Blvd. until it intersected Red Cliffs Rd. From there, U.S. 91 went in a north-east direction, with Red Cliffs becoming Telegraph St. in Washington. U.S. 91 followed on Telegraph until becoming Main St. in Leeds. After leaving Leeds, Old 91 is still intact until about about a half mile north of the junction with SR-228 where its routing runs right into I-15. 
From Anderson Junction to Springville US-91 is in the shadows of I-15. At places the old pavement is visible off to the side of the freeway; at others I-15 was paved over the old US-91.
US-91 first joined U.S. Route 89 in Springville at one of the oldest grade-separated interchanges in Utah (this portion is now State Route 51). From this junction to Logan the two highways ran mostly concurrent. This portion is mostly intact as US-89.
US-91 did have a unique route between Farmington and Ogden and where US-89/91 split and then rejoined on what is now State Route 126 and State Route 26. These highways form the Main Street through Kaysville and Layton; State Street from the Layton-Clearfield border to Main Street in Clearfield though the city of Sunset turning into 1900 West at the Sunset-Roy border, then following 1900 W to a junction with Riverdale Road in Roy, then following Riverdale Road through Riverdale, and then meeting back up with US-89 at Washington Blvd in Ogden.
U.S. 91 formerly entered Idaho Falls along Yellowstone Highway, and returned to the course of modern I-15 north of town. The highway then proceeded north toward Monida Pass where the highway entered Montana. In some small towns streets used by the route are called "Old Highway 91".
In Montana the highway's alignment slightly changed with the construction of the Clark Canyon Dam. In Dillon the former route of the highway is now known as Atlantic Street and Montana Street. North of Dillon I-15 was built on a new alignment. The highway formerly joined with U.S. Route 10 in Butte and formed the main street of Boulder. The highway was routed through Helena along what is now Montana Secondary Highway 518 and Montana Secondary Highway 229.
Major intersections 
||Brigham City||0.000||0.000||I-15 / I-84 – Ogden, Tremonton|
|1.965||3.162||US-89 south / SR-13 north – Brigham City, Willard||South end of US 89 overlap|
|3.920||6.309||SR-90 west – Brigham City||Grade separated interchange; westbound exit and eastbound entrance|
|Mantua||5.601||9.014||Mantua Road||Grade separated interchange; eastbound exit and westbound entrance|
||Wellsville||16.939||27.261||SR-23 north – Mendon|
|19.177||30.862||SR-101 – Hyrum|
|23.769||38.252||SR-252 north (1000 West)|
|Logan||26.651||42.891||SR-165 south – Hyrum, Nibley|
|26.886||43.269||SR-30 west – Tremonton|
|27.148||43.690||US-89 north – Garden City, Utah State University, Bear Lake||North end of US 89 overlap|
|North Logan||29.819||47.989||SR-252 south|
|Smithfield||34.021||54.751||SR-218 west – Newton|
|Richmond||40.004||64.380||SR-142 west – Trenton|
|43.694||70.319||SR-61 west – Lewiston|
|Utah/Idaho state line|
||Preston||8.389||13.501||SH-36 west – Weston||South end of SH-36 overlap|
|9.265||14.911||SH-34 north / SH-36 east – Montpelier, Soda Springs||North end of SH-36 overlap|
|I-15 – Pocatello, Malad||South end of I-15 overlap (mileposts begin reflecting distance along I-15)|
|US 91 overlaps with I-15 (exits 36–67)|
|I-15 / I-15 Bus. / US-30||North end of I-15 overlap (mileposts end reflecting distance along I-15)
South end of I-15 Bus. overlap (mileposts begin reflecting distance along I-15 Bus.)
|3.442||5.539||US-30 west||North end of US 30 overlap|
|I-15 Bus.||North end of I-15 Bus. overlap (mileposts end reflecting distance along I-15 Bus.)|
|Chubbuck||80.020||128.780||I-86 – Twin Falls, Boise|
|I-15 – Pocatello, Idaho Falls||South end of I-15 Bus. overlap (mileposts begin reflecting distance along I-15 Bus.)|
|I-15 Bus. – Pocatello, Idaho Falls||North end of I-15 Bus. overlap (mileposts end reflecting distance along I-15 Bus.)|
|York Road/Old I-15 Bus.||Mileposts begin reflecting distance along old I-15 Bus. alignment|
|Idaho Falls||4.526||7.284||I-15 Bus. / US-26 – Idaho Falls||Mileposts end reflecting distance along old I-15 Bus. alignment|
See also 
- U.S. Department of Agriculture (1926). United States System of Highway (Map).
- Sum of Utah and Idaho milage logs in the Major intersections section of this article
- "Highway Resolution route 91". Utah Department of Transportation. Retrieved 2008-03-08.
- "Utah Code". State of Utah. Retrieved 2007-12-11.
- H.M. Gousha Company (1967). Road Atlas (hosted by Broer Map Library) (Map). p. 42. http://www.broermapsonline.org/members/NorthAmerica/UnitedStates/NorthernRockies/gousha_ra_1967_024.html. Retrieved 2008-01-27.
- Benchmark Maps (2002). Utah Road and Recreation Atlas (Map). 1:250000 (2002 ed.). p. 80, section G3. ISBN 0-929591-74-7. http://www.benchmarkmaps.com.
- "Google Maps, northern Idaho". Google Maps. Retrieved 2008-03-09.
- "Google Maps, Dillon Montana". Google Maps. Retrieved 2008-03-09.
- "Highway Reference Information". Utah Department of Transportation. Retrieved 2011-09-19.
- "Idaho Transportation Department Milepost Log State Highway System: US 91 Main Route". Idaho Transportation Department. 2011-08-26. Retrieved 2012-06-10.
- "Idaho Transportation Department Milepost Log State Highway System: Interstate 15 Main Route". Idaho Transportation Department. 2011-08-26. Retrieved 2012-06-10.
|Browse numbered routes|
|← SR-90||UT||SR-92 →|
|← US-89||ID||US-93 →|
|← I-90||MT||US 93 →|
|Wikimedia Commons has media related to: U.S. Route 91|