U.S. Route 20 in Idaho

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This article is about the section of U.S. Route 20 in Idaho. For the entire route, see U.S. Route 20.

U.S. Highway 20 marker

U.S. Highway 20

Map
US 20 highlighted in red
Route information
Maintained by ITD
Length411 mi[1] (661 km)
Existed1940[2]–present
Major junctions
West end US 20 / US 26 at the Oregon state line
Major intersections
East end US 20 at the Montana state line
Location
CountryUnited States
StateIdaho
CountiesPayette, Canyon, Ada, Elmore, Camas, Blaine, Butte, Bingham, Bonneville, Jefferson, Madison, Fremont
Highway system
  • Idaho State Highway System
← SH-19→ SH-21

U.S. Route 20 (US-20) is the portion of an east–west U.S. Highway in the state of Idaho. It begins northwest of Parma at the Oregon state line and ends at least 9.6 miles (15.4 km) away from the Yellowstone National Park west entrance at the Montana state line.

Route description

I-15/US-20 Jct. in Idaho Falls, ID

US 20 crosses into Idaho northwest of Parma, running concurrently with US 26 and joins US 95 through Parma. US 20/US 26 leaves US 95 southeast of Parma and runs to Caldwell where US 20/US 26 joins with I-84 and US 30 for a short time. These four highways parallel each other (on two roadways) to Boise where US 20/US 26 runs through downtown before joining with I-84 and US 30 again to Mountain Home, where it departs at exit 95 to head east, past Rattlesnake Station, Anderson Ranch Dam road, and cresting at Cat Creek summit at 5,527 feet (1,685 m) above mean sea level. It continues into and across Camas County through Fairfield to Timmerman Junction, the intersection in Blaine County with State Highway 75, the route to Sun Valley, Galena Summit, and Stanley. US 20 continues east through Picabo and Carey, joined with US 26 and US 93, to Craters of the Moon 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 the Idaho National Laboratory, where the highways split just west of Atomic City; US 26 heads 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.[2]

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.[3]

Junction list

CountyLocationmi[4]kmExitDestinationsNotes
Snake River0.0000.000
 US 20 / US 26 west – Nyssa		Continuation into Oregon
Snake River Bridge; Oregon–Idaho state line
Payette​1.5782.540
 US 95 north – Fruitland, Payette		Western end of US-95 concurrency
Canyon​9.64715.525
 US 95 south – Jordan Valley		Eastern end of US-95 concurrency
Caldwell21.995–
22.129		35.398–
35.613
 I-84 / US 30 west – Ontario		Western end of I-84/US-30 concurrency; I-84 exit 26
27

 I-84 BL east to SH-19 – Caldwell, Wilder, Homedale		Exit numbers follow I-84
2810th Avenue – City Center
24.840–
24.994		39.976–
40.224
 I-84 / US 30 east – Nampa, Boise		Eastern end of I-84/US-30 concurrency; I-84 exit 29
Ada​34.26755.147 SH-16 – Emmett
Boise–Eagle line40.22964.742 SH-55 – Caldwell, Eagle
Garden City44.16671.078 SH-44 – Eagle
BoiseMain StreetWest end of freeway; westbound entrance only
47.30076.122—

 I-184 west to I-84		Eastern terminus of I-184; westbound left exit and eastbound left entrance
48.05077.329—River StreetEastbound exit only
—Front Street westEast end of freeway; westbound exit only
51.97583.646Federal WayInterchange
52.560–
52.664		84.587–
84.754
 I-84 / US 30 west – NampaModule:Jct warning: "road" parameter is deprecated		Western end of I-84/US-30 concurrency; I-84 exit 54
57 SH-21 (Gowen Road) – Idaho CityExit numbers follow I-84
​59S. Eisenman Road / Memory RoadSigned as exits 59A (S. Eisenman Rd.) and 59B (Memory Rd.) eastbound
​64Blacks Creek Road – Kuna
Regina71Mayfield, Orchard
Elmore​74Simco Road
​90


 I-84 BL east to SH-51 / SH-67 – Mountain Home, Bruneau		Eastbound signage
West Mountain HomeWestbound signage
Mountain Home95.066–
95.307		152.994–
153.382

 I-84 / US 26 / US 30 west / 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
CamasFairfield SH-46 – Gooding, Wendell
Blaine​ SH-75 – Shoshone, Challis
Carey US 26 / US 93 – Bliss, Twin FallsWestern end of US-26/US-93 concurrency
ButteArco US 93 – ChallisEastern end of US-93 concurrency
Butte City SH-33 – Howe
Atomic City US 26 – Idaho FallsEastern end of US-26 concurrency
Bingham
 No major junctions
BonnevilleIdaho Falls


 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

 I-15 north – Roberts, Butte, Airport		Signalized interchange; eastern end of I-15 concurrency; I-15 exit 119; access to airport via Grandview Avenue
West end of Rigby Freeway
—Lindsay Boulevard
—Riverside Drive – City Center
—Science Center DriveEastbound exit and westbound entrance
​310
 US 20 Bus. – Lewisville
Orvin311Saint Leon Road / 15th East
​313Hitt Road / 25th East
Ucon315 SH-43 – Ucon
Bonneville–Jefferson
county line		​318County Line Road
JeffersonRigby320

 US 20 Bus. to SH-48 – Rigby		Eastbound exit and westbound entrance
322
 US 20 Bus. – North Rigby


 US 20 Bus. to SH-48 – Rigby
Eastbound signage

Westbound signage
Lorenzo325Menan, Roberts
Snake RiverBridge
Madison​328Thornton
Rexburg332BYU-Idaho, South Rexburg
333 SH-33 – Salmon, Rexburg
337North Rexburg
Sugar City338Sugar City, SalemEastbound exit and westbound entrance
339

 To SH-33 east – Driggs, Jackson, Sugar City		East end of Rigby Freeway
Fremont​344South St. AnthonyAt-grade intersection; no exit number southbound
St. Anthony346

 US 20 Bus. east – St. Anthony		Interchange
​

 US 20 Bus. west – St. Anthony
Ashton
 SH-47 to SH-32 – Driggs
Island Park SH-87 – Ennis
Continental DivideTarghee Pass; Idaho–Montana state line

 US 20 east – West Yellowstone, Bozeman		Continuation into Montana
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

References

  1. ^ Google (February 29, 2016). "Snake River to Yellowstone National Park" (Map). Google Maps. Google. Retrieved February 29, 2016.
  2. ^ a b 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. ^ "Thornton Interchange opens, U.S. 20 improvements now complete". East Idaho News. November 18, 2016. Retrieved July 16, 2018.
  4. ^ "Milepoint Log — State Highway System" (PDF). Idaho Transportation Department. Retrieved April 15, 2016.

External links

KML file (edit • help)
Template:Attached KML/U.S. Route 20 in Idaho
KML is not from Wikidata


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