|Maintained by WYDOT|
|Length||434.003 mi (698.460 km)|
|Restrictions||Intermittent closures during winter|
|West end||Eastern entrance of Yellowstone National Park|
|East end||US 20 at Nebraska state line|
|Counties||Park, Big Horn, Washakie, Hot Springs, Fremont, Natrona, Converse, Niobrara|
U.S. Highway 20 (US 20) is an east–west highway in the state of Wyoming. The eastern segment of US 20 in the state starts at the eastern entrance to Yellowstone National Park along with the western terminuses of US 14 and US 16. US 14/US 16/US 20 runs east to Greybull, where US 14 continues east and US 16/US 20 turns south; at Worland, US 16 turns east while US 20 continues south, passing through Wind River Canyon south of Thermopolis. US 20 joins US 26 in Shoshoni, where it turns east and continues all the way through Casper. From Casper, US 20/US 26 parallels Interstate 25 (I-25) and US 87 for 26 miles (42 km), until all four link up together just southeast of Glenrock. I-25/US 20/US 26/US 87 stays combined to Orin, where US 20 turns east from I-25, at the western end of US 18. US 18/US 20 run concurrently from Orin to Lusk, where US 18 turns north and US 20 continues east into Nebraska.
Yellowstone National Park
Unofficially, Google Maps marks the start of the western part of US 20, along with US 191 and US 287, at the state line near West Yellowstone, Montana. The road parallels the Madison River until a junction with US 89. The three routes then turn south along US 89 (Grand Loop Road), paralleling the Firehole River. Past Old Faithful, the four routes curve east before reaching the West Thumb of Yellowstone Lake. While the rest of the routes turn south, US 20 travels northeast along the lake. US 20 even leaves the Grand Loop Road at an intersection midway along the lake. This intersection also marks the western "terminuses" of US 14 and US 16. US 20 travels through for 65.8 miles (105.9 km) by the time it exits the park.
Yellowstone–Nebraska state line
The eastern section of US 20 begins at the east entrance of Yellowstone National Park. US 20, along with US 14 and US 16, then meanders east along the Shoshone River, heading toward Wapiti, Buffalo Bill Reservoir, and Cody. US 14A begins at Cody and continues to follow the river, while the three head straight to Greybull. Before Greybull, however, Wyoming Highway 789 (WYO 789) joins the concurrency. At Greybull, US 14 leaves the concurrency. At this point, the concurrency parallels the Bighorn River. In Worland, US 16 turns east and leaves the concurrency. South of the Boysen Dam, the road runs along the eastern front of the Boysen Reservoir. In Shoshoni, US 20 turns east along US 26, while WYO 789 turns west along the same route.
As US 20 and US 26 head toward Casper, the two routes travel along a limited-access road before traveling east along I-25 and US 87. US 20, US 26, and US 87 exit onto Beverly Street (exit 186) and travel east along Yellowstone Highway. Before reaching Glenrock, the three U.S. Highways are sandwiched between the North Platte River to the north and I-25 to the south. The three routes rejoins the interstate after Glenrock. US 20 leaves the freeway at Orin; this interchange is also where US 18 begins eastward. US 87 briefly joins the concurrency before US 20 turns east away from US 18/US 85. After passing through Van Tassell, US 20 crosses the Nebraska state line.
US 20 became a U.S. Highway in 1926. Prior to 1940, it ended at Yellowstone National Park. In 1940, it was extended westward to Albany, Oregon; however, as U.S. Highways are not formally designated in national parks such as Yellowstone, US 20 can be thought of as made up of two parts broken by Yellowstone National Park.
|Yellowstone National Park||0.000||0.000||East Entrance Road||Continuation into Yellowstone National Park; US 20 resumes in Montana at the park's west entrance|
|Yellowstone National Park boundary (East Entrance); fees required|
Western end of US 14 and US 16 overlaps
|Park||Pahaska Tepee||2.000||3.219||Westbound road closure gate (closed winters)|
|Cody||49.410||79.518||WYO 291 (South Fork Road)|
US 14A east / WYO 120 west – Powell, Big Horn Natl Rec Area
|Western end of WYO 120 overlap|
WYO 120 south – Meeteetse, Thermopolis
|Eastern end of WYO 120 overlap|
|Big Horn||||85.056||136.884||WYO 30 – Burlington|
|Emblem||85.665||137.864||WYO 32 – Powell, Lowell|
US 310 west / WYO 789 north – Lovell
|Western end of WYO 789 overlap|
US 14 east – Shell, Sheridan
|Eastern end of US 14 overlap|
|||109.910||176.883||WYO 36 (Golf Course Road)|
|Basin||112.765||181.478||WYO 30 – Burlington|
|Manderson||113.782||183.114||WYO 31 – Manderson, Hyattville|
US 16 east – Buffalo
|Eastern end of US 16 overlap; access to Washakie Medical Center|
To WYO 432 (Railroad Ave)
WYO 431 west / WYO 432 east
|Hot Springs||||164.032||263.984||WYO 175 – Kirby|
|||168.825||271.698||WYO 172 (Black Mountain Road)|
|Thermopolis||176.083||283.378||WYO 120 – Meeteetse, Cody, Wyoming Dinosaur Center||Access to Hot Springs Memorial Hospital|
|||178.727||287.633||WYO 173 (Buffalo Creek Road)|
|||180.991||291.277||Eastbound road closure gate (weather depending)|
|Fremont||||205.123||330.113||Westbound road closure gate (weather depending)|
US 26 west / WYO 789 south – Riverton
|Eastern end of WYO 789 overlap; western end of US 26 overlap|
|209.053||336.438||Eastbound road closure gate (weather depending)|
|Moneta||229.753||369.752||Eastbound road closure gate (weather depending)|
|Natrona||||255.323||410.903||Waltman rest area|
|||295.633||475.775||Westbound road closure gate (weather depending)|
US 20 Bus. / US 26 Bus. / WYO 257 to WYO 220 – Casper, Rawlins
|||304.547||490.121||WYO 254 (Salt Creek Highway) – Casper Point of Entry|
I-25 north / US 87 north – Sheridan
|Western end of I-25 and US 87 overlaps|
|306.267||492.889||188B||Poplar Street (WYO 220)|
I-25 BL / US 87 Bus. east / WYO 255 south (Center Street)
|No northbound entrance; western terminus of I-25 Bus./US 87 Bus.; WYO 255 unsigned|
I-25 south – Cheyenne
|Eastern end of I-25 overlap|
WYO 258 south (Curtis Street) to I-25
WYO 256 north / WYO 253 south to I-25
WYO 95 north – Rolling Hills
I-25 BL west
|Western end of I-25 BL overlap|
|||335.188||539.433||I-25 road closure gate (weather depending)|
I-25 north / I-25 BL ends – Casper
|Western end of I-25 overlap; eastern end of I-25 BL overlap|
|||345.142||555.452||151||Ayres Natural Bridge|
WYO 96 east (La Prele Road)
I-25 BL south (US 20 Bus. / US 26 Bus. / US 87 Bus.) to WYO 59 – Douglas, Gillette
I-25 BL north (US 20 Bus. / US 26 Bus. / US 87 Bus.) – Douglas
I-25 south / US 26 east / US 87 south / US 18 begins – Glendo
|Eastern end of I-25, US 26, and US 87 overlaps; western end of US 18 overlap|
WYO 319 south
|Eastbound road closure gate (weather depending)|
|Niobrara||||401.555||646.240||Westbound road closure gate (weather depending)|
|Manville||402.546||647.835||WYO 270 – Manville, Lance Creek, Guernsey|
|||409.535||659.083||Westbound road closure gate (weather depending)|
|||410.055||659.920||Lusk rest area|
WYO 273 north
US 85 south – Torrington
|Southern end of US 85 overlap|
US 18 east / US 85 north – Newcastle
|Eastern end of US 18 overlap; northern end of US 85 overlap|
|412.615||664.039||Eastbound road closure gate (weather depending)|
US 20 east – Harrison
|Continuation into Nebraska|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|
- State Maintenance Engineer’s Office (October 1, 2017). "Maintenance Section Reference Book" (PDF). Wyoming Department of Transportation. Retrieved May 31, 2021.
- Google (January 1, 2023). "Yellowstone National Park" (Map). Google Maps. Google. Retrieved January 1, 2023.
- National Park Service (July 2022). Yellowstone National Park (PDF) (Map). National Park Service. p. 1. Retrieved January 1, 2023.
- Google (July 15, 2022). "West Yellowstone, Montana" (Map). Google Maps. Google. Retrieved July 15, 2022.
- Google (July 15, 2022). "US 20 at Yellowstone" (Map). Google Maps. Google. Retrieved July 15, 2022.
- Google (July 15, 2022). "Overview Map of US 20 (WY; non-Yellowstone)" (Map). Google Maps. Google. Retrieved July 15, 2022.
- Bureau of Public Roads & American Association of State Highway Officials (November 11, 1926). United States System of Highways Adopted for Uniform Marking by the American Association of State Highway Officials (Map). 1:7,000,000. Washington, DC: United States Geological Survey. OCLC 32889555. Retrieved December 31, 2022 – via Wikimedia Commons.
- Executive Committee (June 3, 1940). "Addenda to Minutes of Executive Committee" (PDF) (Report). Washington, DC: American Association of State Highway Officials. Retrieved December 31, 2022 – via Wikimedia Commons.
- Lew, Josh (February 5, 2021). "Take a Classic Road Trip on America's Longest Highway". Treehugger. Retrieved July 15, 2022.
- Media related to U.S. Route 20 in Wyoming at Wikimedia Commons