The present route of US 2 follows several wagon roads that were built in the late 19th century by local railroad companies, including the Stevens Pass Highway along the Skykomish River.

A series of projects is planned to improve the US 2 corridor between Snohomish and Skykomish by expanding the highway near various cities and the completion of a bypass around Monroe.

[13][14] US 2 turns south and crosses over the Pilchuck River and the Centennial Trail before its limited-access road ends at a diamond interchange with 88th Street.

[19][20][21] US 2, now part of a National Scenic Byway named the Stevens Pass Greenway,[22][23] continues through the city of Monroe and forms the northern terminus of SR 203.

The highway enters Mount Baker-Snoqualmie National Forest and continues east along the Tye River past the town of Skykomish and the Cascade Tunnel towards Stevens Pass.

[25][26] The highway continues east down Nason Creek to Coles Corner, the southern terminus of SR 207, which serves Lake Wenatchee.

US 2 travels due south along the Wenatchee River valley through Leavenworth before it begins a 27-mile-long (43 km) concurrency with US 97 at a diamond interchange east of Peshastin.

US 2 and US 97 split at Orondo, with US 97 continuing north along the Columbia River towards Chelan and US 2 traveling east up Pine Canyon onto the Waterville Plateau.

The highway travels through the town of Waterville via several turns on city streets before heading due east across the Columbia Plateau, intersecting SR 172 at Farmer.

[61] A proposal from representatives of the highway departments of Idaho and Washington to extend US 2 to Everett was considered by the AASHO's U.S. Route Numbering Committee in January 1946, but was vetoed.

The proposal resurfaced during the committee's meeting on December 20, 1946, and was approved as a replacement of US 10 Alternate from Everett to Bonners Ferry and US 195 from Spokane to Newport.

[3] US 2 was re-routed around various cities over the next several decades onto limited-access highways to reduce congestion, beginning with the construction of the current westbound Hewitt Avenue Trestle east of Everett, which opened on April 8, 1969.

[65][66][67] US 2 was routed north of Wenatchee onto the Olds Station Bridge, renamed in 1991 to honor Richard Odabashian, over the Columbia River in 1975,[68] while the former alignment was designated as SR 285 in 1977.

[69] The present two-lane expressway north and east of Snohomish was approved in 1969 and opened in October 1983;[70][71] it was originally intended to also include an unfinished bypass of Monroe.

[74][75] Within Newport, US 2 had an unsigned spur route that traveled on the southbound lanes of ID-41 on the Idaho state line until 1997, when SR 41 was created to avoid confusion.

[79] In the early 2000s, WSDOT began planning a series of 56 projects to improve the US 2 corridor between Snohomish and Skykomish, where the highway is two lanes wide and has been the site of over 2,600 collisions between 1999 and 2007 that caused 47 fatalities.

The study suggested the expansion of the limited-access highway from Snohomish to the western city limits of Monroe to four lanes,[82] including an interchange at Bickford Avenue that was later completed in September 2013.

[88] Seasonal traffic congestion in the Sultan area, which causes backups that overflow onto side streets, have inspired proposals to build an additional bypass, a two-street couplet, or a freeway along the Stevens Pass corridor.

[90] In addition to the freeway expansion, WSDOT is considering a total replacement of the westbound Hewitt Avenue Trestle that would cost between $750 million to $1 billion.

[91] One of the options in the early feasibility study conducted in 2017 included a vehicle toll, which sparked public outcry on social media.