U.S. Route 12 (US 12) is a major east–west U.S. Highway, running from Aberdeen, Washington, to Detroit, Michigan. It spans across the state of Washington, making it the second longest highway in the state. It is also the only numbered highway to span the entire state from west to east, starting near the Pacific Ocean, and crossing the Idaho state line near Clarkston. It crosses the Cascade Range over White Pass, south of Mount Rainier National Park. Portions of it are concurrent with Interstate 5 (I-5) and Interstate 82 (I-82), although the majority of the route does not parallel any interstate highway. The route is also entirely concurrent with I-82's auxiliary route, Interstate 182.
Although US 12 was not extended into Washington until 1967, portions of it have been part of Washington's state highway system since as early as 1905. The last part of the highway to open was over White Pass in 1951, although it was added to the state highway system by the legislature in 1931. Most of the route (except for the approximately between Elma and Naches) had been part of the U.S. Highway System since its inception in 1926 as part of U.S. Route 410. The portion between Napavine and Grand Mound was also designated a U.S. Highway in 1926 as part of U.S. Route 99.
Route description
US 12 begins in downtown Aberdeen on the Pacific Coast as a pair of one-way streets: Heron Street for eastbound traffic and Wishkah Street for westbound traffic. The streets travel from the highway's western terminus at US 101, which continues west to Hoquiam and south to Cosmopolis, across the Wishkah River and merge onto Wishkah Street near a shopping center. US 12 leaves Aberdeen and follows the Chehalis River east through Central Park as a four-lane divided highway. The highway bypasses the towns of Montesano and Elma, which are served by interchanges as well as a junction with SR 107 in the former.
In Elma, US 12 exits at a diamond interchange, while the highway continues east to Olympia as SR 8. US 12 heads southeast towards Oakville and Rochester, still following the Chehalis River. East of Oakville, US 12 runs north of the Chehalis Indian Reservation. It then continues east through the town of Rochester, and interchanges with I-5 at exit 88 in the town of Grand Mound.
US 12 continues south concurrent with I-5 through Chehalis and Centralia before exiting again at exit 68 south of Napavine. The highway then heads east along the Cowlitz River and passes through the town of Mossyrock, where it intersects SR 122. East of Mossyrock, US 12 runs just north of Mossyrock Dam and Riffe Lake. In the town of Morton, it intersects SR 7, which heads north to Tacoma. It then ascends the Cascade Range, passing south of Mount Rainier, and intersects SR 123, which serves the Stevens Canyon entrance of Mount Rainier National Park. east of this intersection, US 12 crosses the Cascades over White Pass at an elevation of . White Pass is the only crossing of the Cascades open year-round between I-90 over Snoqualmie Pass and SR 14 through the Columbia River Gorge.
After it descends the mountains, US 12 intersects SR 410 (formerly US 410) west of Naches, which serves Chinook Pass, Cayuse Pass, and the White River entrance of Mount Rainier National Park. East of Naches, US 12 widens once again to four lanes as it approaches the city of Yakima. There, it has an interchange with I-82 and US 97 at exit 31. US 12 then runs concurrently with I-82, bypassing the towns of Toppenish and Prosser and paralleling the Yakima River, until exit 102 near the Tri-Cities. At exit 102, it meets the western terminus of Interstate 182. US 12 and I-182 then run concurrently east over Goose Gap and through the Tri-Cities. In Pasco, I-182 ends, and US 12 intersects US 395.
US 12 then heads south to the town of Wallula, intersecting US 730, then east to Walla Walla, north to Dodge, and east to Clarkston before crossing the Idaho state line over the Snake River just outside Lewiston. US 12 through Walla Walla consists of a four-lane bypass, also known as Inland Empire Highway. The alignment of US 12 through Walla Walla County passes by a number of historical landmarks, such as Whitman Mission and Fort Walla Walla.
History The Washington section of US 12 was originally developed as a state highway in the early 20th century. It was incorporated into several later highways, including US 410.
Early years
The Washington State Legislature created the State Highway Board in 1905 and appropriated funds to construct—but not maintain—twelve highways in sparsely settled areas of the state. Main highways in more populated areas would continue to be entirely under county control, though sometimes built with 50% state funding. Six of these highways were east-west crossings of the Cascades, including one in the corridor currently served by U.S. Route 12—State Road 5, the Cowlitz Pass State Road, climbing east from a point near Salkum via the Cowlitz River, over Cowlitz Pass, and down towards Yakima.: "(5) For the building of a State wagon road in Yakima and Lewis Counties, as follows, to-wit: Beginning at a point in the center of the public highway running from the town of Napavine to Klickitat prairie in Lewis County, Washington, at the point nearest to the south-east corner of Section 10 in Township 12, north of Range 1, east of Willamette meridian, and running thence by way of Klickitat prairie and Riffe Postoffice in a generally easterly course up the Cowlitz river and its tributaries to the summit of the Cascade mountains at the Cowlitz pass, thence easterly towards the town of North Yakima to a point in Yakima County, intersecting with a public highway leading to the town of North Yakima, said road to be known and designated as the Cowlitz Pass State road, the sum of $26,000." A 1907 amendment renamed State Road 5 the Cowlitz-Natches Road, moved the Cascade crossing north to Carlton Pass, and defined the portion east of the pass to follow the Bumping River and Naches River to a point near Naches. East of the mouth of the American River, this replaced part of State Road 1 (North Yakima and Natches State Road), which had been defined in 1897 to cross the Cascades north of Chinook Pass and included in the 1905 appropriations.: "State Road No. 5, or the Cowlitz-Natches road: This road shall begin at a point in the center of the public highway running from the town of Napavine to Klickitat prairie in Lewis county, Washington, at the point nearest to the southeast corner of section 10, in township 12, north of range 1 east W. M., and shall run thence over the present surveyed line on such state road, by the way of Klicitat[sic] prairie and Riffe postoffice up the Cowlitz river and its tributaries, and over the summit of the Cascade mountains at the Carlton pass; thence over such surveyed line for said road down Bumping river and the Natches river to a point which bears south 73 degrees and 24 minutes east and is distant from the corner of sections 27, 28, 33 and 34, in township 15, north range 16, east W. M., in Yakima county, Washington."
Under a 1909 law, the State Highway Board surveyed a connected network of proposed state roads. Included was a westerly extension of SR 5 via Chehalis to South Bend and Aberdeen and an easterly extension to Pullman. A route from Yakima southeast and east via the Tri-Cities to Idaho was also surveyed, mostly as an extension of State Road 8 (Columbia River Road).: "2nd. Extension over the most feasible route of State Road No. 5 westerly through the city of Chehalis to the cities of South Bend in Pacific county and Aberdeen in Chehalis county, and easterly to the city of Pullman in Whitman county." "3rd. Extension over the most feasible route of State Road No. 8 westerly to the city of Vancouver and easterly to the city of Walla Walla and thence to the eastern boundary of Asotin county." "6th. A road beginning at a point on the proposed extension of State Road No. 7 in the vicinity of Cle Elum in Kittitas county, leading thence as nearly as practicable along the Yakima valley to an intersection with the proposed extension of State Road No. 8 in Benton county." The legislature added most of these routes to the state highway system in 1913, when they formed a two-tiered system of primary and secondary roads. Primary roads were completely controlled by the state, including maintenance, and received only names, while secondary roads kept their numbers and county maintenance. The National Park Highway replaced State Road 5 west of Riffe, and extended as surveyed to and beyond South Bend, and the McClellan Pass Highway replaced State Road 1 and continued via State Road 5 to Yakima. The majority of the route from Yakima via Connell to Pullman was not added at that time; it was finally taken over in 1937 as Secondary State Highways 11A and 11B. Only the route via the Tri-Cities, forming part of the Inland Empire Highway, continued from Yakima to Idaho. East of Pomeroy, the original survey had curved south, using State Road 16 to near the Oregon state line; this was bypassed by the 1913 designation, which instead continued directly east to Clarkston. Unlike the earlier state roads, these primary roads mostly followed existing passable county roads. The incomplete roadway between Riffe and the American River remained as part of secondary State Road 5, and the legislature designated the surveyed route from the National Park Highway near Raymond north to Aberdeen as secondary State Road 20 in 1915.
A 1923 restructuring of the system reassigned numbers to almost all the primary state highways. State Road 5 became a primary route and was greatly expanded, taking over the entire McClellan Pass Highway and the National Park Highway east of the Pacific Highway. The former secondary State Road 5 was realigned starting from near Packwood, heading north instead of east, alongside the Ohanapecosh River to the old McClellan Pass Highway at Cayuse Pass, west of the summit of the Cascades. The new State Road 5, named the National Park Highway System, now included four roads in the vicinity of Mount Rainier National Park, but as the road across the Cascades at Chinook Pass was not yet built, these roads did not connect with each other. Also included in this numbering was the designation of the Inland Empire Highway, including Yakima to Clarkston, as State Road 3.: "A primary state highway, to be known as State Road No. 5 or the National Park Highway System, is established as follows: Beginning at the City of Tacoma; thence by the most feasible route in a southeasterly direction through Elbe and Ashford to the Rainier National Park gate; also from a junction in the City of Elbe; thence in a southerly direction through Morton, Kosmos; thence in a westerly direction through Nesika, Riffe and Ethel to a junction with State Road No. 1 or the Pacific Highway at or in the vicinity of Jackson Prairie; also, from a junction at or near Kosmos in Lewis County in a northeasterly direction through Lewis in Lewis County through Sheepskull Gap; thence in a northwesterly direction through Enumclaw, Auburn, Kent to a connection with State Road No. 2 in the vicinity of Renton; also from a junction at Sheepskull Gap in a southeasterly direction to Yakima." In 1925, a spur was added to State Road 9—the Olympic Highway, looping around the Olympic Peninsula—connecting Elma to the Pacific Highway at Grand Mound, and creating a shortcut between the Cowlitz River route and Aberdeen. The Olympic Highway from Elma west to Aberdeen had been added to the state highway system in 1905 west of and 1913 east of Montesano.
U.S. Route 410