Interstate 15 in Idaho

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Interstate 15

I-15 highlighted in red
Route information
Maintained by ITD
Length196.000 mi[1] (315.431 km)
NHSEntire route
Major junctions
South end I-15 at the Utah state line near Woodruff
Major intersections
North end I-15 at the Montana state line at Monida Pass
CountryUnited States
CountiesOneida, Bannock, Bingham, Bonneville, Jefferson, Clark
Highway system
  • Idaho State Highway System
SH-14 SH-16

Interstate 15 (I-15) is a part of the Interstate Highway System that runs from San Diego, California, to Sweetgrass, Montana. In Idaho, the Interstate Highway runs exactly 196 miles (315 km) from the Utah state line near Woodruff north to the Montana state line at Monida Pass. I-15 is the primary north–south highway of Eastern Idaho. The Interstate Highway connects Pocatello and Idaho Falls, the fourth and fifth largest cities in Idaho, and the smaller county seats of Malad City, Blackfoot, and Dubois. I-15 connects all of those cities with Salt Lake City to the south and Butte to the north. The Interstate has business loops through McCammon, Inkom, Pocatello, Blackfoot, and Idaho Falls.

Route description

I-15 is designated the Veterans Memorial Highway for its entire length in Idaho.

Woodruff to Pocatello

I-15 enters Oneida County from Box Elder County, Utah, south of the hamlet of Woodruff. The four-lane freeway heads north parallel to the Union Pacific Railroad's Malad Subdivision rail line, a road named Old Highway 191, and the Malad River along the eastern edge of the wide Malad Valley adjacent to the Malad Range. I-15 has a diamond interchange with Woodruff Road at Woodruff and follows the western edge of Caribou National Forest. The highway passes just to the east of the county seat, Malad City, where the highway has a diamond interchange with the eastern end of Idaho State Highway 38 (SH 38). I-15 continues along Deep Creek to another diamond interchange with the western end of SH 36. From there, the freeway follows the narrow valley of Devil Creek between the Bannock Range to the east and Elkhorn Mountain to the west. I-15 has one more diamond interchange in Oneida County next to Devils Creek Reservoir before the highway reaches Malad Summit, where the highway leaves the Great Salt Lake watershed and enters the Snake River watershed.[2]

I-15 enters Bannock County and descends into the Marsh Valley, named for Marsh Creek, which the highway begins to parallel at its diamond interchange with SH 40, which heads east toward Downey. At a diamond interchange at the hamlet of Virginia, the freeway begins to run concurrently with U.S. Route 91 (US 91) and parallel Union Pacific's Pocatello Subdivision rail line and Old Highway 91. I-15 and US 91 have diamond interchanges with Arimo Road just west of Arimo and with the southern end of I-15 Bus. south of McCammon. At the north end of McCammon, the freeway reconnects with its business route and is joined by US 30. I-15 heads north through Indian Rocks State Park along a ridge between Marsh Creek to the west and the Portneuf River to the east, then crosses the Portneuf River just east of its confluence with Marsh Creek.[2]

I-15 crosses over the rail line and Old Highway 91 as it curves west to follow the narrow valley of the Portneuf River between the Bannock Range to the south and the Pocatello Range to the north. The highway has partial interchanges with I-15 Bus. on either side of the tiny city of Inkom. I-15 begins to curve north at its four-ramp partial cloverleaf interchange with Old Highway 91 at Portneuf shortly before entering the city of Pocatello. US 30 and US 91 split off from the freeway at the next interchange, a diamond interchange with Fifth Avenue that marks the southern end of Pocatello's I-15 Bus. I-15 veers away from the rail line and the Portneuf River, has a diamond interchange with Clark Street east of downtown Pocatello, and collects the other end of I-15 Bus. at its diamond interchange with Pocatello Creek Road. The freeway leaves the city of Pocatello at its directional T interchange with I-86. I-15 passes along the eastern edge of the city of Chubbuck, which is accessed using I-86.[2]

Pocatello to Monida Pass

I-15/US 20 Jct. in Idaho Falls, ID

I-15 continues north onto the Snake River Plain and into the Fort Hall Indian Reservation. The highway accesses the reservation's main settlement, Fort Hall, via a diamond interchange with Ross Fork Road on the Bannock–Bingham county line. I-15 has a four-ramp partial cloverleaf interchange with US 91, at which the highway crosses over Union Pacific's Montana Subdivision rail line, near the northern edge of the reservation; I-15 Bus. splits northeast with US 91 from this interchange. The freeway curves northeast and crosses the Blackfoot River and begins to parallel the Snake River as it passes along the western edge of the city of Blackfoot. I-15 Bus. reconnects with I-15 at a diamond interchange with US 26 (Bridge Street), which runs concurrently with the freeway leaving Blackfoot. The highway crosses the Snake River at the northern edge of the city. I-15 has a partial cloverleaf interchange near Rose before it crosses a pair of irrigation canals. The freeway then travels across the eastern part of the Hell's Half Acre Lava Field ahead of its interchange with River Road, which provides access to Shelley east of the Snake River.[2]

In Bonneville County, US 26 and I-15 Bus. split off onto Sunnyside Road shortly before I-15 enters Idaho Falls. The freeway has a five-ramp partial cloverleaf interchange with US 20 (West Broadway Street), from which US 20 Bus. splits east concurrent with I-15 Bus., which returns to the mainline Interstate. I-15 and US 20 run concurrently to a four-ramp partial cloverleaf interchange where US 20 heads northeast as a freeway towards Rexburg and Yellowstone National Park. The freeway heads north out of Idaho Falls parallel to the Montana Subdivision rail line, Old Highway 91, and the Snake River. I-15 enters Jefferson County just north of its diamond interchange with Osgood Road, and the freeway diverges from the Snake River at Roberts, where it has a diamond interchange with the western end of SH 48.[2]

I-15 passes Market Lake Wildlife Management Area ahead of its diamond interchange with SH 33 at Sage Junction. The highway has a diamond interchange with Hamer Road at Hamer and briefly passes through the Camas National Wildlife Refuge and crosses Camas Creek, which flows into Mud Lake. I-15 follows a tributary of Camas Creek, Beaver Creek, into Clark County and its county seat of Dubois, where the freeway meets the eastern end of SH 22 at a diamond interchange. North of Dubois, the freeway has a partial cloverleaf interchange with Sheep Station Road that serves the U.S. Sheep Experiment Station. I-15 continues along Beaver Creek through a diamond interchange at Spencer as the freeway enters the Bitterroot Range. The freeway enters Targhee National Forest and has diamond interchanges with Stoddard Creek Road and at Humphrey. I-15 reaches its northern end in Idaho at Monida Pass, where the highway crosses the Continental Divide into Beaverhead County, Montana.[2]


Two major sections of I-15 were opened in late 1965: the Arimo to McCammon section in October and the Inkom to South Pocatello section in November.[3][4] The freeway was extended around Pocatello on August 5, 1966.[5]


Reconstruction of the interchange with I-86 in Chubbuck began in August 2022 and is scheduled to be completed in 2025 at a cost of $112 million.[6] The new design eliminates left-side ramps from I-15 and allows traffic from the Pocatello Creek Road interchange to merge onto either freeway.[7][8] A new interchange to the north at New Day Parkway was opened in December 2019 as part of Chubbuck's Northgate development.[9]

Exit list

I-15 south (Veterans Memorial Highway) – Salt Lake City
Continuation into Utah
Woodruff2.544.093Woodruff Road – Woodruff, Samaria
Malad City12.88820.74113
SH-38 west – Malad
SH-36 east (Deep Creek Road) – Weston, Preston
21.52334.63822Colton Lane – Devil Creek Reservoir
SH-40 east (Woodland Road) – Downey, Preston
US 91 south – Downey, Preston
South end of concurrency with US-91
Arimo40.46265.11740Arimo Road – Arimo
I-15 BL north (Jensen Road) – McCammon

I-15 BL south / US 30 east – McCammon, Lava Hot Springs, Soda Springs, Montpelier
South end of concurrency with US-30
I-15 BL north – Inkom
Northbound exit, southbound entrance
I-15 BL south – Inkom
Southbound exit, northbound entrance
Portneuf63.037101.44863Portneuf Road – Portneuf Area

I-15 BL north / US 30 west / US 91 north (Fifth Avenue)
North end of concurrencies with US-30 and US-91
69.396111.68269Clark Street
I-15 BL south (Pocatello Creek Road) – Pocatello
I-86 west – Chubbuck, Twin Falls
I-86 exits 63A-B; tri-stack directional T interchange; former I-15W
73.480118.25573Northgate Parkway, New Day Parkway
county line
Fort Hall79.903128.59180Ross Fork Road – Fort Hall
I-15 BL north / US 91 – Blackfoot

I-15 BL south / US 26 west / SH-39 – Blackfoot, Arco, Aberdeen
South end of concurrency with US-26
Rose97.681157.20298Lambert Road – Rose, Firth
107.990173.793108River Road – Shelley Area
BonnevilleWoodville113.212182.19711365th South – Shelley
Idaho Falls115.890186.507116

I-15 BL north / US 26 east (Sunnyside Road) – Ammon, Jackson
North end of concurrency with US-26

I-15 BL south / US 20 Bus. east (Broadway Street east) / US 20 west (Broadway Street west) – Historic Downtown, Arco
South end of concurrency with US-20
US 20 east – Rigby, West Yellowstone, Airport, Idaho Falls
North end of concurrency with US-20
127.525205.232128Osgood Road – Osgood Area
SH-48 east – Roberts, Rigby
Sage Junction143.003230.141143 SH-33 / Weigh Station – Rexburg, Salmon, Mud LakeSigned separately southbound as unnumbered exit (Weigh Station) and exit 143 (SH-33)
Hamer149.609240.772150Hamer Road – Hamer
SH-22 west / CR A2 – Dubois
171.974276.765172Ranch Exit
Spencer180.389290.308180Spencer Road – Spencer
184.407296.774184Stoddard Creek Road – Stoddard Creek Area
Humphrey189.857305.545190Humphrey Road – Humphrey
Continental Divide
(Monida Pass)
196.000315.431IdahoMontana line

I-15 north – Butte
Continuation into Montana
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

Business routes

I-15 has five Interstate business loops in McCammon, Inkom, and Pocatello in Bannock County, as well as in Blackfoot in central Bingham County and Idaho Falls in western Bonneville County. Some of these routes are overlapped by segments of US 91.


  1. ^ a b "Milepoint Log - State Highway System - I-15" (PDF). Idaho Transportation Department. October 23, 2014. Archived from the original (PDF) on April 2, 2015. Retrieved March 1, 2015.
  2. ^ a b c d e f Google (February 12, 2023). "Interstate 15 in Idaho" (Map). Google Maps. Google. Retrieved February 12, 2023.
  3. ^ "Arimo to McCammon Interstate Due to Open". Idaho State Journal. Pocatello, Idaho. October 3, 1965. p. 1. Retrieved July 15, 2018 – via
  4. ^ "Interstate 15 Opening Set For Wednesday". Idaho State Journal. Pocatello, Idaho. November 2, 1965. p. 7. Retrieved July 15, 2018 – via
  5. ^ "Ceremonies, Speeches Open Newest Stretch of Interstate". Idaho State Journal. Pocatello, Idaho. August 5, 1966. p. 2. Retrieved July 15, 2018 – via
  6. ^ Harris, Shelbie (August 1, 2022). "'Historic investment': Gov. Little, state officials highlight aging bridges during 'Flying Y' groundbreaking". Idaho State Journal. Pocatello, Idaho. Retrieved February 12, 2023.
  7. ^ "$111.9 million Contract Awarded for Pocatello System Interchange" (Press release). Idaho Transportation Department. May 24, 2022. Retrieved February 12, 2023.
  8. ^ O'Connell, John (December 18, 2021). "ITD prepares to bid $100 million overhaul of 'Flying Y' interchange". Idaho State Journal. Pocatello, Idaho. Retrieved February 12, 2023.
  9. ^ O'Connell, John (December 8, 2019). "Fruits of cooperation: Officials laud partnership that led to new I-15 interchange". Idaho State Journal. Pocatello, Idaho. Retrieved February 12, 2023.

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