U.S. Route 20 in Idaho

U.S. Highway 20 marker
U.S. Highway 20
U.S. Highway 20 marker U.S. Highway 20
Idaho Medal of Honor Highway
	US 20 highlighted in red
Route information
	Maintained by ITD
Length	406.30 mi (653.88 km)
Existed	1940–present
Major junctions
West end	File:US 20.svgFile:US 26.svg US 20 / US 26 at the Oregon state line
	File:US 95.svg US 95 in Parma; File:I-84.svgFile:US 30.svg I-84 / US 30 in Caldwell; File:I-84.svgFile:US 30.svg I-84 / US 30 in Garden City; File:I-84.svgFile:US 26.svgFile:US 30.svg I-84 / US 26 / US 30 in Mountain Home; File:US 26.svg US 26 in Carey; File:US 26.svgFile:US 93.svg US 26 / US 93 in Atomic City; File:I-15.svg I-15 in Idaho Falls;
East end	File:US 20.svg US 20 at the Montana state line
Location
Country	United States
State	Idaho
Counties	Payette, Canyon, Ada, Elmore, Camas, Blaine, Butte, Bingham, Bonneville, Jefferson, Madison, Fremont
Highway system
	United States Numbered Highway System; List; Special; Divided; Idaho State Highway System; Interstate; US; State;

U.S. Highway 20 (US 20) is the portion of an east–west United States Numbered Highway in the state of Idaho. It begins northwest of Parma at the Oregon state line and enters Montana 9.6 miles (15.4 km) away from the Yellowstone National Park west entrance. Since 2019, US 20 has been designated as the Idaho Medal of Honor Highway.^[3]

Route description

File:I 15 US 20 Junction Sign.jpg

I-15/US 20 junction in Idaho Falls

At the western border, adjacent to Nyssa, Oregon, US 20 (running concurrently with US 26) crosses the Snake River into Idaho at an approximate elevation of 2,200 feet (670 m) above sea level. It joins US 95 and runs southbound to Parma. US 20/US 26 leaves US 95 southeast of Parma and runs to Caldwell, where it briefly joins Interstate 84 (I-84; and US 30) from exit 26 until exit 29. These four highways parallel each other east (on two roadways) to Boise where US 20/US 26 runs through downtown, then southbound on Broadway Avenue to rejoin with I-84/US 30 at exit 54. The four concurrent routes head southeast to Mountain Home, where US 20 departs at exit 95 to head east, past Rattlesnake Station, Anderson Ranch Dam road, and crests at Cat Creek summit at 5,527 feet (1,685 m). This portion of the route is near Goodale's Cutoff of the Oregon Trail. US 20 continues east, into, and across Camas County through Fairfield to Timmerman Junction, the intersection in Blaine County with State Highway 75 (SH-75), the northbound route to Sun Valley, Galena Summit, and Stanley. US 20/US 26 goes through Picabo and Carey, joins with US 93, and on to Craters of the Moon National Monument and Preserve and Arco, where US 93 splits off and turns north-northwest to climb the Big Lost River valley. US 20/US 26 continues on through Idaho National Laboratory, where the highways split just west of Atomic City; US 26 heads southeast to Blackfoot and US 20 to Idaho Falls, where it turns north-northeast to pass near Rexburg as a freeway. US 20 then climbs through the communities of St. Anthony, Ashton, and Island Park, and crosses the Continental Divide at Targhee Pass at 7,072 feet (2,156 m), entering Montana west of West Yellowstone.

History

US 20 was expanded past Yellowstone National Park in 1940, replacing the original US 191 and several state highways.^[2] Its original alignment through Boise included Main Street and Fairview Avenue for westbound and eastbound traffic, respectively, and Capitol Boulevard. US 20 and US 26 were realigned onto Myrtle and Front streets as well as Broadway following the completion of the Boise Connector extension on August 7, 1992.^[4]^[5] The Rigby Freeway section of US 20, extending from Idaho Falls to St. Anthony, was constructed in the 1970s. Its northernmost section still featured at-grade intersections until the 2000s, when they were replaced with full interchanges,^[6] though a few at grade crossings still exist between Sugar City and St. Anthony as of September 2023.

Major intersections

County	Location	mi^[1]	km	Exit	Destinations	Notes
Snake River		0.000	0.000		File:West plate.svg File:US 20.svgFile:West plate.svg File:US 26.svg US 20 west / US 26 west – Nyssa	Continuation into Oregon
Snake River		0.000	0.000		Snake River Bridge; Oregon–Idaho state line
Payette		1.578	2.540		File:North plate.svg File:US 95.svg US 95 north – Fruitland, Payette	Western end of US 95 concurrency
Canyon		9.647	15.525		File:South plate.svg File:US 95.svg US 95 south – Jordan Valley	Eastern end of US 95 concurrency
	Caldwell	21.995– 22.129	35.398– 35.613		File:I-84.svgFile:West plate.svg File:US 30.svg I-84 / US 30 west – Ontario	Western end of I-84/US 30 concurrency; I-84 exit 26
				27	File:East plate green.svg File:Business Loop 84.svgFile:To plate.svg File:Idaho 19.svg I-84 BL east to SH-19 – Caldwell, Wilder, Homedale	Exit numbers follow I-84
				28	10th Avenue – City Center	Exit numbers follow I-84
		24.840– 24.994	39.976– 40.224		File:I-84.svgFile:East plate.svg File:US 30.svg I-84 / US 30 east – Nampa, Boise	Eastern end of I-84/US 30 concurrency; I-84 exit 29
Ada		34.267	55.147		File:Idaho 16.svg SH-16 – Emmett
	Boise–Eagle line	40.229	64.742		File:Idaho 55.svg SH-55 – Caldwell, Eagle
	Garden City	44.166	71.078		File:Idaho 44.svg SH-44 – Eagle
	Boise				Main Street	Western end of freeway; westbound entrance only
		47.300	76.122	—	File:West plate blue.svg File:I-184.svgFile:To plate blue.svg File:I-84.svg I-184 west to I-84	Eastern terminus of I-184; westbound left exit and eastbound left entrance
		48.050	77.329	—	River Street	Eastbound exit only
				—	Front Street west	Eastern end of freeway; westbound exit only
		51.975	83.646		Federal Way	Interchange
		52.560– 52.664	84.587– 84.754		File:I-84.svgFile:West plate.svg File:US 30.svg I-84 / US 30 west / Commerce Avenue – Nampa	Western end of I-84/US 30 concurrency; I-84 exit 54
				57	File:Idaho 21.svg SH-21 (Gowen Road) – Idaho City	Exit numbers follow I-84
				59	S. Eisenman Road, Memory Road	Signed as exits 59A (S. Eisenman Road) and 59B (Memory Road) eastbound
				64	Blacks Creek Road – Kuna
	Regina			71	Mayfield, Orchard
Elmore				74	Simco Road
				90	File:East plate green.svg File:Business Loop 84.svgFile:To plate.svg File:Idaho 51.svgFile:To plate.svg File:Idaho 67.svg I-84 BL east to SH-51 / SH-67 – Mountain Home, Bruneau	Eastbound signage
				90	West Mountain Home	Westbound signage
	Mountain Home	95.066– 95.307	152.994– 153.382		File:I-84.svgFile:US 26.svgFile:East plate.svg File:US 30.svgFile:West plate green.svg File:Business Loop 84.svg I-84 / US 26 / US 30 east / I-84 BL west (SH-51) – Mountain Home, Twin Falls, Air Force Base, Duck Valley	Eastern end of I-84/US 26/US 30 concurrency; I-84 exit 95
Camas	Fairfield				File:Idaho 46.svg SH-46 – Gooding, Wendell
Blaine					File:Idaho 75.svg SH-75 – Shoshone, Challis
Blaine	Carey				File:US 26.svgFile:US 93.svg US 26 / US 93 – Bliss, Twin Falls	Western end of US 26/US 93 concurrency
Butte	Arco				File:US 93.svg US 93 – Challis	Eastern end of US 93 concurrency
	Butte City				File:Idaho 33.svg SH-33 – Howe
	Atomic City				File:US 26.svg US 26 – Idaho Falls	Eastern end of US 26 concurrency
Bingham	No major junctions
Bonneville	Idaho Falls				File:South plate blue.svg File:I-15.svgFile:Business Loop 15.svgFile:Business plate.svg File:US 20.svgFile:To plate.svg File:US 26.svg I-15 south / I-15 BL / US 20 Bus. (Broadway Street east) to US 26 – Blackfoot, Pocatello, Jackson, Idaho Falls	Western end of I-15 concurrency; I-15 exit 118
					File:North plate blue.svg File:I-15.svgFile:Airport Sign.svg I-15 north – Roberts, Butte, Airport	Eastern end of I-15 concurrency; I-15 exit 119; access to airport via Grandview Avenue; signalized interchange
					Western end of Rigby Freeway
					307	Lindsay Boulevard
				308A	Riverside Drive – City Center	Signed as Exit 308 eastbound
				308B	Science Center Drive	Eastbound exit and westbound entrance
				310	File:Business plate.svg File:US 20.svg US 20 Bus. – Lewisville
	Orvin			311	Saint Leon Road, 15th East
				313	Hitt Road, 25th East
	Ucon			315	File:Idaho 43.svg SH-43 – Ucon
Bonneville–Jefferson county line				318	County Line Road
Jefferson	Rigby			320	File:Business plate.svg File:US 20.svgFile:To plate.svg File:Idaho 48.svg US 20 Bus. to SH-48 – Rigby	Eastbound exit and westbound entrance
				322	File:Business plate.svg File:US 20.svg US 20 Bus. – North Rigby	Eastbound signage
				322	File:Business plate.svg File:US 20.svgFile:To plate.svg File:Idaho 48.svg US 20 Bus. to SH-48 – Rigby	Westbound signage
	Lorenzo			325	Menan, Roberts
Snake River				Bridge
Madison				328	Thornton
	Rexburg			332	BYU-Idaho, South Rexburg
				333	File:Idaho 33.svg SH-33 – Salmon, Rexburg
				337	North Rexburg
	Sugar City			338	Sugar City, Salem	Eastbound exit and westbound entrance
	Sugar City			339	File:To plate.svg File:East plate.svg File:Idaho 33.svg To SH-33 east – Driggs, Jackson, Sugar City	Eastern end of Rigby Freeway
Fremont				344	South St. Anthony	New interchange under construction
	St. Anthony			346	File:East plate.svg File:Business plate.svg File:US 20.svg US 20 Bus. east – St. Anthony	Interchange
					File:West plate.svg File:Business plate.svg File:US 20.svg US 20 Bus. west – St. Anthony
	Ashton				File:Idaho 47.svgFile:To plate.svg File:Idaho 32.svg SH-47 to SH-32 – Driggs
	Island Park				File:Idaho 87.svg SH-87 – Ennis
Continental Divide					Targhee Pass; Idaho–Montana state line
Continental Divide					File:East plate.svg File:US 20.svg US 20 east – West Yellowstone, Bozeman	Continuation into Montana
1.000 mi = 1.609 km; 1.000 km = 0.621 mi Concurrency terminus Incomplete access Route transition

References

↑ ^1.0 ^1.1 "Milepoint Log — State Highway System: US 20" (PDF). Idaho Transportation Department. January 25, 2016. Retrieved February 10, 2023.
↑ ^2.0 ^2.1 Weingroff, Richard (October 17, 2013). "Ask the Rambler: What Is the Longest Road in the United States?". Federal Highway Administration. Retrieved December 4, 2014.
↑ Blanchard, Nicole (March 25, 2019). "This Idaho road is now the Medal of Honor Highway. Meet the honorees who crossed its path". Idaho Statesman. Retrieved August 27, 2021.
↑ "Drivers ease on down Boise's new roadway". The Idaho Statesman. August 8, 1992. p. 1A. Retrieved February 10, 2023 – via Newspapers.com.
↑ "Regular Meeting of the Idaho Transportation Board, August 27, 1992" (PDF). Idaho Transportation Department. August 27, 1992. p. 35. Retrieved February 10, 2023.
↑ "Thornton Interchange opens, U.S. 20 improvements now complete". East Idaho News. November 18, 2016. Retrieved July 16, 2018.

External links

KML file (edit • help)

Template:Attached KML/U.S. Route 20 in Idaho

KML is not from Wikidata

File:US 20.svg U.S. Route 20
Previous state: Oregon	Idaho	Next state: Montana

[milepoint-1] 1.0 ^1.1 "Milepoint Log — State Highway System: US 20" (PDF). Idaho Transportation Department. January 25, 2016. Retrieved February 10, 2023.

[fhwa-2] 2.0 ^2.1 Weingroff, Richard (October 17, 2013). "Ask the Rambler: What Is the Longest Road in the United States?". Federal Highway Administration. Retrieved December 4, 2014.

[3] Blanchard, Nicole (March 25, 2019). "This Idaho road is now the Medal of Honor Highway. Meet the honorees who crossed its path". Idaho Statesman. Retrieved August 27, 2021.

[4] "Drivers ease on down Boise's new roadway". The Idaho Statesman. August 8, 1992. p. 1A. Retrieved February 10, 2023 – via Newspapers.com.

[5] "Regular Meeting of the Idaho Transportation Board, August 27, 1992" (PDF). Idaho Transportation Department. August 27, 1992. p. 35. Retrieved February 10, 2023.

[6] "Thornton Interchange opens, U.S. 20 improvements now complete". East Idaho News. November 18, 2016. Retrieved July 16, 2018.

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U.S. Route 20 in Idaho

Contents

Route description

History

Major intersections

References

External links

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