US 12 in Idaho

By | October 18, 2022


US 12
Begin Lewiston
End Lolo Pass
Length 172 mi
Length 278 km





US 12 is a US Highway in the US state of Idaho. The road forms an east-west route through the north of the state, from the Washington border at Lewiston through the Rocky Mountains to Lolo Pass on the border with Montana. The route is 278 kilometers long.

  • ElectronicsMatter: State facts of Idaho, covering history, geography, demography, economics, politics, and administrative division of Idaho.

Travel directions

The Snake River Bridge in Lewiston on the Oregon border.

US 12 near Lolo Pass.

In the town of Lewiston, US 12 in Washington from Walla Walla enters the state of Idaho and then passes through the city of 31,000 inhabitants. The border is formed by the important Snake River. US 12 then heads east and crosses the Clearwater River, creating a short double number with US 95, the road from Coeur d’Alene in the north to the capital Boise in the south. The road then follows a scenic route through a shallow canyon to the east. This part of Idaho is still somewhat populated with quite a few villages and small towns in the area. The largest town on the rest of the route is the town of Orofino, with a population of 3,000. There are no other crossings for the rest of the routeUS Highways more, some state routes. The road then curves slightly south, following the Clearwater River valley. From Kooskia, the road turns east and enters the Clearwater Mountains. The road then follows the Lochsa River and the landscape quickly becomes more mountainous. The surrounding mountains reach up to about 2100 meters. This is the Clearwater National Forest. The valley of the Lochsa River is quite narrow, with uninhabited side valleys. The road then has virtually no side roads over long distances. There are hardly any villages on the route and the road is fairly quiet, but still a through route. The road winds a lot and is not a fast route. Meanwhile, it is also slowly rising. One then reaches the 1595 meter high Lolo Pass on the border with Montana. The US 12 in Montanathen continues to the city of Missoula.

  • Fun-wiki: Brief information of the state Idaho, covering basic history and geography as well as top cities of Idaho.


US 12 was created in 1926, but was not yet expiring in Idaho at the time. In 1962, the route was extended west from Missoula, Montana, to Lewiston, Idaho. This followed road completion in Idaho that year. US 12 was built during World War II by inmates of the Kooskia Internment Camp. In 1967, a further extension followed in Washington state. The Lolo Pass section was not built until the 1960s and was the last US Highway to be built. The eastern portion of US 12 runs through very remote territory, with no places on the route for more than 100 miles.

US 12 originally ran through downtown Kooskia. A two-mile bypass north of the Clearwater River was constructed in 1963 and opened on September 25, 1963.

Traffic intensities

Every day, 6,200 vehicles drive between the Washington and Lewiston border and 22,000 vehicles in Lewiston itself. East of Lewiston there are still 11,000 vehicles on the four-lane section, which drops to 3,400 vehicles to Orofino to the east and 1,800 to 2,000 vehicles to Kooskia. The long section from Lowell to the Montana border only handles about 550 vehicles per day.

US 12 in Idaho