Interstate 15 in Idaho

Interstate 15
Route information
Maintained by ITD
Length:	196.000 mi[1] (315.431 km)
Major junctions
South end:	I-15 at the Utah state line near Woodruff
	US-91 near Arimo US-30 near McCammon I-86 in Pocatello US-26 in Blackfoot US-20 in Idaho Falls
North end:	I‑15 at the Montana state line at Monida Pass
Location
Counties:	Oneida, Bannock, Bingham, Bonneville, Jefferson, Clark
Highway system
Interstate Highway System Main Auxiliary Suffixed Business State Highways in Idaho ← 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 Interstate 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 Interstate 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.

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 Interstate 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 Interstate 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.

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 Interstate 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 Interstate 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.

Pocatello to Monida Pass

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 Interstate 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 Interstate 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 Interstate 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.

I-15 enters Bonneville County at its interchange with West 65th Street South near Woodville, which is simply given the destination of "Exit 113" northbound. US 26 and I-15 Bus. split off onto Sunnyside Road shortly before I-15 enters Idaho Falls. The Interstate has a five-ramp partial cloverleaf interchange with US 20 (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 toward Rigby, Rexburg, and Yellowstone National Park. The Interstate 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.

I-15 passes Market Lake Wildlife Management Area ahead of its diamond interchange with SH 23 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 Interstate 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 Interstate enters the Bitterroot Range. The Interstate 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.

Exit list

County	Location	mi[1]	km	Exit	Destinations	Notes
Oneida	​	0.000	0.000	—	I-15 south (Veterans Memorial Highway) – Salt Lake City	Southern terminus of I-15 in Idaho; Utah state line
	Woodruff	2.54	4.09	3	Woodruff Road – Woodruff, Samaria
	Malad City	12.888	20.741	13	SH-38 west – Malad
	​	16.55	26.63	17	SH-36 east (Deep Creek Road) – Weston, Preston
	​	21.523	34.638	22	Colton Lane – Devil Creek Reservoir
Bannock	​	30.884	49.703	31	SH-40 east (Woodland Road) – Downey, Preston
	Virginia	35.900	57.775	36	US-91 south – Downey, Preston	South end of concurrency with US-91
	Arimo	40.462	65.117	40	Arimo Road – Arimo
	​	44.075	70.932	44	I-15 Business Loop north (Jensen Road) – McCammon
	McCammon	47.164	75.903	47	I-15 Business Loop south / US-30 east – McCammon, Lava Hot Springs, Soda Springs, Montpelier	South end of concurrency with US-30
	Inkom	56.646	91.163	57	I-15 Business Loop north – Inkom	Northbound exit, southbound entrance
		57.694	92.849	58	I-15 Business Loop south – Inkom	Southbound exit, northbound entrance
	Portneuf	63.037	101.448	63	Portneuf Road – Portneuf Area
	Pocatello	66.806	107.514	67	I-15 Business Loop north / US-30 west / US-91 north (Fifth Avenue)	North end of concurrencies with US-30 and US-91
		69.396	111.682	69	Clark Street
		71.000	114.263	71	I-15 Business Loop south (Pocatello Creek Road) – Pocatello
	Chubbuck	72.121	116.067	72	I-86 west – Chubbuck, Twin Falls	I-86 exits 63A-B
Bannock–Bingham county line	Fort Hall	79.903	128.591	80	Ross Fork Road – Fort Hall
Bingham	​	88.764	142.852	89	I-15 Business Loop north / US-91 – Blackfoot
	Blackfoot	92.525	148.905	93	I-15 Business Loop south / US-26 west / SH-39 – Blackfoot, Arco, Aberdeen	South end of concurrency with US-26
	Rose	97.681	157.202	98	Lambert Road – Rose Firth
	​	107.990	173.793	108	River Road – Shelley Area
Bonneville	Woodville	113.212	182.197	113	West 65th Street South – Shelley	Signed destination is "Exit 113" northbound
	Idaho Falls	115.890	186.507	116	I-15 Business Loop north / US-26 east (Sunnyside Road) – Ammon, Jackson	North end of concurrency with US-26
		118.543	190.776	118	I-15 Business Loop south / US-20 west / US-20 Business east (Broadway Street) – Historic Downtown, Arco	South end of concurrency with US-20
		119.098	191.670	119	US-20 east (Rigby Highway) – Rigby, West Yellowstone, Idaho Falls, Airport	North end of concurrency with US-20
	​	127.525	205.232	128	Osgood Road – Osgood Area
Jefferson	Roberts	134.568	216.566	135	SH-48 east – Roberts, Rigby
	Sage Junction	143.003	230.141	143	SH-33 – Mud Lake, Rexburg, Salmon
	Hamer	149.609	240.772	150	Hamer Road – Hamer
Clark	Dubois	167.038	268.822	167	SH-22 west / CR-A2 – Dubois
	​	171.974	276.765	172	Sheep Station Road	Signed destination is "No Services"
	Spencer	180.389	290.308	180	Spencer Road – Spencer
	​	184.407	296.774	184	Stoddard Creek Road – Stoddard Creek Area
	Humphrey	189.857	305.545	190	Humphrey Road – Humphrey
	Monida Pass	196.000	315.431	—	I‑15 north – Butte	Northern terminus of I-15 in Idaho; Montana state line
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus       Incomplete access

Business routes

I-15 has five Interstate business loops in Idaho:

• Interstate 15 Business (McCammon, Idaho) has a length of 4.338 miles (6.981 km) through McCammon in central Bannock County. I-15 Bus. begins at I-15 Exit 44 along Jensen Road, then turns north and follows State Street to the city of McCammon. Just north of the city limits, the business route veers onto Center Street and follows that through the center of town. At the north end of the city, I-15 Bus. turns west and runs concurrently with US 30 to its northern end at I-15 Exit 47.
• Interstate 15 Business (Inkom, Idaho) runs for exactly 1 mile (1.6 km) through Inkom in northern Bannock County. I-15 Bus. mostly follows Old Highway 91 between Exits 57 and 58, a pair of partial interchanges.
• Interstate 15 Business (Pocatello, Idaho) spans 5.560 miles (8.948 km) through Pocatello in northern Bannock County. I-15 Bus. begins at I-15 Exit 67, where US 30 and US 91 also diverge from I-15. The business route and the U.S. Highways follow Fifth Street northwest. The routes split onto a one-way pair of Fifth Street northbound and Fourth Street southbound. The highways pass by Idaho State University and through downtown Pocatello. At the north end of downtown, I-15 Bus. and the U.S. Highways veer north and converge as Pocatello Avenue. US 30 turns west at Oak Street; the business route and US 91 continue north along Yellowstone Avenue. I-15 Bus. leaves US 91 when it turns east onto Alameda Road, which becomes Pocatello Creek Road when it veers northeast to the business route's terminus at I-15 Exit 71.
• Interstate 15 Business (Blackfoot, Idaho) has a length of 4.802 miles (7.728 km) through Blackfoot in central Bingham County. I-15 Bus. begins at I-15 Exit 89 near the northern end of the Fort Hall Indian Reservation and follows US 91 northeast parallel to the Union Pacific Railroad. The highways cross the Blackfoot River into the city of Blackfoot along Broadway Street. In downtown Blackfoot, the routes veer onto Main Street, then I-15 Bus. turns northwest onto a one-way pair, Bridge Street northbound and Judicial Street southbound. The streets converge as Bridge Street, which the business route follows to its end at I-15 Exit 93. The roadway continues beyond the interchange as US 26 and immediately crosses the Snake River.
• Interstate 15 Business (Idaho Falls, Idaho) runs for 3.409 miles (5.486 km) through Idaho Falls in western Bonneville County. I-15 Bus. begins at I-15 Exit 116, which is also where US 26 diverges from the Interstate. The business route and U.S. Highway follow Sunnyside Road across the Snake River to Yellowstone Avenue; this intersection forms the northern terminus of US 91. I-15 Bus. and US 26 follow Yellowstone Avenue northeast parallel to the Union Pacific Railroad into downtown Idaho Falls. At the intersection of Yellowstone Avenue and Broadway Street, I-15 Bus. turns northwest onto Broadway Street and runs concurrently with US 20 Bus. across another bridge over the Snake River to their mutual termini at I-15 Exit 118. The roadway continues west as US 20.

References

1. "Milepoint Log - State Highway System - I-15" (PDF). Idaho Transportation Department. October 23, 2014. Retrieved 2015-03-01.