List of Idaho State Highways

The Idaho Transportation Department is responsible for the establishment and classification of a state highway network which includes the interstate highways, U.S. highways, and state routes. These routes are listed below.

History

Instead of numbering its highways, Idaho had a system of lettered Sampson Trails in the 1920s.^[1] They were marked by Charles B. Sampson of Boise at no expense to the state.^[2] By the mid-1930s, the state had adopted a more standard system of numbered state highways.^[3]^[4]

The following trails were marked:^[1]

A, Boise to Wyoming via Twin Falls and Pocatello; became US-30 and US-30N
B, Boise to Canada via Lewiston and Coeur d'Alene; became US-30, US-30N, US-95, and SH-1
C, Pocatello to Montana via Idaho Falls; became US-91 and US-191
D, Boise to New Meadows via Banks; became SH-15 (today's SH-55)
E, not on the 1926 map
F, Boise to Blackfoot via Stanley; became SH-21, SH-17, US-93 (today's SH-75), and SH-27
G, Mountain Home to Picabo via Fairfield; became SH-22 (today's US-20)
H, Bliss to Trude via Arco; became SH-24, SH-23, SH-22, SH-29, and an unnumbered road (today's US-20 and US-26)
I, Pioneer to Idaho Falls; became an unnumbered road
J, Nevada to Shoshone via Twin Falls; became US-93
K, Utah to McCammon via Preston; became US-91
L, not on the 1926 map
M, Washington to Montana via Coeur d'Alene; became US-10
N, Bonners Ferry to Montana; became US-2
O, Oregon to Caldwell; became SH-49 and SH-18
P, Utah to Downey; became SH-36
Q, Declo to Fairfield; became SH-25 and SH-46
R, not on the 1926 map
S, Oregon to Nampa; became unnumbered road and SH-45
T, Star to Grimes Pass; became SH-16, unnumbered road, and SH-17
U, Utah to Montpelier; became SH-35
V, Hailey to Stanley; became US-93 (today's SH-75)
W, not on the 1926 map
X, not on the 1926 map
Y, Bonners Ferry to Canada; became US-95

Interstates

	Interstate 15	At 200 miles (320 km) in length, it traverses through Pocatello, Blackfoot, and Idaho Falls.
	Interstate 84	Crossing through the "heel" of the Idaho "boot", this interstate passes through Boise, near Twin Falls, and other smaller towns.
	Interstate 86	Located entirely within Idaho, it stretches from Interstate 84 in Heyburn to Interstate 15 at Pocatello.
	Interstate 90	The 73-mile (117 km) segment of interstate highway boasted one of the last traffic lights on the interstate highway system at Wallace.
	Interstate 184	This spur connects Interstate 84 travelers to downtown Boise.

U.S. Highways

	US-2
	US-10	Replaced by Interstate 90. Interstate 90 Business in Coeur d'Alene, Osburn/Silverton, Post Falls, and Wallace are segments of US-10.
	US-12	Runs from the Washington border in Lewiston to the Montana border at Lolo Pass.
	US-20	There's a freeway like section in eastern Idaho from Idaho Falls to Chester.
	US-26
	US-30	mostly Concurrent with Interstate 84 and Interstate 86
	US-30N	Renumbered U.S. Route 95 Spur
	US-30S
	US-89
	US-91
	US-93	Runs from Jackpot, Nevada to Lost Trail Pass in Montana. Concurrency with US 26 from Shoshone to Arco.
	US-95	Currently being upgraded to a freeway like highway for safety and for a faster and easier way to connect the 2 most populous Metro areas in Idaho.
	US-95E
	US-95W
	US-191
	US-195
	US-287	Section in Idaho renamed Idaho Highway 87
	US-410	Renumbered U.S. Route 12
	US-630	Renumbered as U.S. Route 95 Spur in Weiser

State highways

	SH-1	Connects US-95 to the Canadian border at Porthill.
	SH-3	Runs from Nez Perce County north to I-90 in Kootenai County.
	SH-4	A six-mile (10 km) road from Wallace to the ghost towns of Gem and Burke.
	SH-5	A short road from Plummer to St. Maries.
	SH-6	Connects State Highway 3 to the Washington border near Potlatch.
	SH-7	Serves the communities of Orofino and Ahsahka.
	SH-8	Runs from the Washington border at Moscow to Elk River.
	SH-9	Connects State Highway 6 at Princeton to State Highway 8 at Deary.
	SH-11	A road through Weippe and Pierce in Clearwater County.
	SH-13	Runs from Kooskia to downtown Grangeville.
	SH-14	Entirely in Idaho County, it connects Grangeville to Elk City.
	SH-16	A short route from Star to Emmett. A freeway like corridor is planned to extend SH-16 to I-84 West.
	SH-19	A valley road from Caldwell to the Oregon border near Homedale.
	SH-21	Runs from the east end of Boise to Stanley.
	SH-22	A route from Dubois to Butte County, where it joins State Highway 33.
	SH-24	In south-central Idaho from Burley to Shoshone.
	SH-25	Runs near Interstate 84 from Jerome to the Declo area.
	SH-27	Connects the town of Oakley to Burley and Paul.
	SH-28	Runs from Salmon to Interstate 15 near the Continental Divide.
	SH-29	A route from Leadore to the nearby Montana border.
	SH-31	In eastern Idaho from Swan Valley to Victor.
	SH-32	An eastern Idaho road from Ashton to Tetonia.
	SH-33	Runs from Butte County to the Wyoming border.
	SH-34	Diverges from State Highway 36 near Preston, and runs to the Wyoming border.
	SH-36	An east-west road from Ovid through Preston to Interstate 15.
	SH-37	Runs from the Oneida/Power county line north to Interstate 86 at American Falls.
	SH-38	Runs east from Holbrook to Malad City and Interstate 15.
	SH-39	A route from Blackfoot to American Falls.
	SH-40	A very short connector from Downey to Interstate 15.
	SH-41	Runs north from Post Falls to the Washington border (near Newport, Washington).
	SH-43	A short route from US Highway 26 north to Ucon.
	SH-44	Cuts across the Treasure Valley from Interstate 84 to Garden City.
	SH-45	Connects State Highway 78 to downtown Nampa.
	SH-46	Runs south from Camas County to Wendell.
	SH-47	A short highway in Fremont County that ends in Ashton.
	SH-48	A route in eastern Idaho from Roberts to Ririe.
	SH-50	Connects US Highway 30 near Kimberly to State Highway 25.
	SH-51	A rural road from Mountain Home south to the Nevada border.
	SH-52	Runs from Horseshoe Bend to the Oregon border at Payette.
	SH-53	Runs west from Rathdrum to the Washington border.
	SH-54	In northern Idaho between Spirit Lake and Bayview.
	SH-55	Begins at Marsing, runs east to Meridian, and turns north to New Meadows.
	SH-57	A route from Priest River to Nordman.
	SH-58	A short continuation of WA 278 to fully connect US Highway 95 to Rockford, Washington.
	SH-60	Runs from US Highway 95 near Plummer to the Washington border.
	SH-61	A one-mile (1.6 km) continuation of WY 89 near Geneva.
	SH-62	A route from Craigmont to Nezperce in north-central Idaho.
	SH-64	Runs east from Nezperce to Kamiah and US Highway 12.
	SH-66	A one-mile (1.6 km) road from US Highway 95, near Viola, that continues into Washington.
	SH-67	A 9-mile (14.4 km) four-lane highway between Mountain Home and Mountain Home Air Force Base.
	SH-69	A short highway from Kuna to Interstate 84 in Meridian.
	SH-71	Connects Cambridge to the Oregon border near Brownlee Dam.
	SH-72	Connects New Plymouth to nearby State Highway 52.
	SH-74	Starts just south of Twin Falls and ends in the downtown area.
	SH-75	Runs from Shoshone through the Sun Valley area to Challis.
	SH-77	Connects US Highway 30 to Malta.
	SH-78	A rural highway from Marsing to Hammett.
	SH-79	A road from US Highway 93 in Twin Falls north to Jerome.
	SH-81	Runs from Malta to Burley.
	SH-87	Runs from US Highway 20 near Henrys Lake to the Montana border.
	SH-97	A route from Harrison to Interstate 90.
	SH-99	A short highway from Troy to Kendrick.
	SH-128	A road in north Lewiston that runs to the Washington border.
	SH-162	A route from Nezperce to Kamiah.
	SH-167	A road between Grand View and Mountain Home Air Force Base.
	SH-200	Pend Oreille Scenic Byway runs east from Ponderay, ID to the Montana border.

References

1 2 Rand McNally Auto Road Atlas, 1926, accessed via the Broer Map Library
↑ Senate Concurrent Resolution No. 8, "a concurrent resolution...to permit Charles B. Sampson to extend the marking system of the Sampson Trail..." passed February 16, 1933
↑ H.M. Gousha Company, Western States road map, published by Standard Oil Company of California, 1935
↑ Rand McNally and Company, Road map: Idaho, Mont., Wyo., published by Texaco, 1937

External links

Numbered highways in the United States

National systems	Interstate Highways U.S. Numbered Highways

State highways	Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming

Other areas	American Samoa District of Columbia Guam Northern Mariana Islands Puerto Rico Virgin Islands

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