U.S. Route 2 (US 2) is a part of the United States Numbered Highway System that has a western segment that runs from Everett, Washington, to the Upper Peninsula of the US state of Michigan. In Washington, it is a state highway that begins at State Route 529 (SR 529) in Downtown Everett. The 326.36 miles (525.23 km) of US 2 that lie within Washington serve as a major conduit. All of the highway within Washington is listed on the National Highway System. Various sections are rural two-lane highway, urbanized four-lane divided expressway and briefly part of Interstate 90 (I-90). The easternmost community along the highway is Newport at the Idaho state line, where the highway continues east into Idaho.

US 2 was extended west from Bonners Ferry, Idaho to Everett in 1946, but the road has been part of Washington's highway system since 1909, with a segment of the highway between Cashmere and Spokane. A Spokane to Newport highway was designated in 1915 and the highways became part of the State Roads in 1923 to be numbered as State Road 2 (Cashmere to Spokane) and State Road 6 (Spokane to Newport). In 1926, the U.S. routes were established and US 10 ran on US 2 between Cashmere and Spokane, while US 195 ran on the highway between Spokane and Newport. In 1931, the final segment of US 2, an Everett to Cashmere highway, was opened in 1931 as State Road 15. In 1937, the State Roads became Primary state highways and the numbers were kept the same as they were earlier. US 10 was realigned onto a southern route in 1940 and the old route between Cashmere and Spokane, along with an extension to Everett, became US 10 Alternate, which merged with US 195 to form the Washington section of US 2 in 1946.

The western terminus of U.S. Route 2 (US 2) is an intersection with State Route 529 (SR 529), named Maple Street, in Downtown Everett. The intersection is located adjacent to a museum and is one block, or 0.19-mile (0.31 km), north of the southern terminus of SR 529 and the Group Health Cooperative Building. From the intersection, US 2 continues eastbound as Hewitt Avenue and westbound as California Street to an interchange with Interstate 5. The interchange, numbered exits 193 and 194, is a directional T and diamond hybrid and serves SR 529, its spur route and two city streets. The highway travels east across the Snohomish River out of Everett onto Ebey Island via the Hewitt Avenue Trestle. Now a two-lane expressway, although the 14-foot (4.27 m) wide eastbound shoulder is open to traffic during afternoons on weekdays since April 2009, the elevated roadway interchanges Homeacres Road and 20th Street SE east of Downtown Everett.

20th Street SE continues in the median of US 2 across Ebey Slough to an interchange with SR 204, a connector to Lake Stevens. After the interchange, the expressway exits the trestle and turns southeast alongside the Ebey Slough to an intersection with Bickford Avenue, former US 2, north of Snohomish, beginning the bypass around Snohomish. After turning east away from the Ebey Slough, the highway interchanges SR 9; the interchange includes a westbound ramp that connects to New Bunk Foss Road, completed in early 2006. The roadway turns southeast to cross the Centennial Trail and the Pilchuck River before an underpass with Three Lakes Road, named for the community of the same name.

In Monroe, the highway is joined by the terminating SR 522, which is the major conduit to Stevens Pass and Leavenworth (and points east) for the Seattle-area population. Another state highway (SR 203) also terminates at US 2 near downtown Monroe and is within one mile (1.6 km) of where SR 522 also terminates. Also in Monroe, the highway starts to parallel the BNSF Railway's Northern Transcontinental rail line. It starts in the Monroe-area and continues for a majority of the way to Wenatchee. This is the western-most section, of many such sections, that US 2 and this railroad route do this, all across the northern United States.

As the highway leaves Monroe to the east, it continues to follow a river valley, only now the river is known as the Skykomish River (one of two rivers that merge near Monroe to create the Snohomish River). The river is within a few feet of the highway on the eastern edge of Monroe.

The highway passes through the communities of Sultan, Startup, and Gold Bar, as the river valley narrows and climbs into the Cascade Mountains. As the highway leaves Gold Bar the character of the road changes to a climbing mountain highway that winds up an increasingly narrow river valley. It passes close to the community of Index, as well as a series of smaller and smaller hamlets. Just before reaching the town of Baring it crosses the county line into King County. As the highway continues up the valley it reaches the community of Skykomish, the last all-season community of any size until east of the Cascades.

Just to the east of Skykomish the river valley the highway is following changes to the Tye River valley. As the highway reaches Scenic, the location of the western portal of the longest railroad tunnel in the world (when it opened in 1929), the Cascade Tunnel, the final climb to Stevens Pass begins.

At the summit of Stevens Pass, elevation 4,061 feet (1,238 m), the highway crosses into Chelan County. Stevens Pass is the location of a world-class ski resort, accessible only by US 2. The Pacific Crest Trail crosses the highway at Stevens Pass.

US 2 then follows the Nason Creek/Wenatchee River valley downstream, eventually passing over the Columbia River just north of Wenatchee. Leaving Wenatchee, US 2 has a 13-mile (21 km) concurrency with US 97, before turning east again at Orondo. The highway continues into the Columbia Plateau, passing Moses Coulee and the Dry Falls Dam portion of Grand Coulee. US 2 continues through rural stretches of Douglas, Grant, and Lincoln Counties before nearing Spokane.

In Spokane, US 2 has an approximately 3-mile (4.8 km) long concurrency with Interstate 90. US 2 exits I-90 at Division Street and then passes through the city, concurrent with US 395. Due to high congestion, the North Spokane Corridor is currently being constructed as a freeway alternate to this route and will carry US 395 upon completion. US 2 will retain the current route on Division Street.

North from downtown US 2 turns to the northeast to reach the town of Newport. US 2 crosses into Idaho immediately east of Newport.

Legally, the Washington section of U.S. 2 is defined at Washington Revised Code § 47.17.005.

The portion of US 2 from the west junction with US 97 near Wenatchee (Peshastin,WA) east to Spokane was originally part of the main highway east from Seattle, which turned north from Cle Elum over Blewett Pass. This was added to the state highway system by the legislature in 1909, as an extension of the Snoqualmie Pass road (State Road 7), and renamed the Sunset Highway (unnumbered) in 1913, then becoming State Road 2 in 1923 and Primary State Highway 2 in 1937. U.S. Route 10 was designated over the entire Sunset Highway from Seattle to Idaho east of Spokane in 1926.

The road now carrying US 2 from Spokane northeast to Newport (on the Idaho state line) was added in 1915 as State Road 23 and renamed the Pend Oreille Highway in 1917. It was extended, in 1921, north along the Pend Oreille River to the international boundary at Nelway, British Columbia and in 1923 the State Road 6 designation was assigned, becoming Primary State Highway 6 in 1937. The original section, from Spokane to Newport, became part of US 195 in 1926.

Finally, the road over Stevens Pass, from Everett to west of Wenatchee (Peshastin to Everett, WA), was not added to the state highway system until 1931. That year, the Stevens Highway, State Road 15, was designated by the legislature; it became Primary State Highway 15 in 1937, but remained marked with only state highway shields until 1940. A branch was added in 1943 (as, also, Primary State Highway 15) branching from the main route near Monroe southwest to Bothell. In 1940, US 10 was shifted off the Sunset Highway between Cle Elum and Spokane, mainly onto existing Primary State Highway 18. At the same time, a new U.S. Route 10 Alternate was created, beginning at US 10 in Seattle and heading north along US 99 to Everett, then turning east via Stevens Pass and former US 10 to Spokane. After intersecting US 10 in Spokane, it turned northeast over US 195 via Newport to Sandpoint, Idaho, and continued east and southeast to US 10 near Missoula, Montana.

In the late 1940s,[when?] most of US 10 Alternate became an extension of US 2 to Everett, which had formerly ended at Bonners Ferry, Idaho (north of Sandpoint, Idaho). US 10 Alternate remained east of Sandpoint, and has since become Idaho State Highway 200 and Montana Highway 200.) The Department of Highways began rebuilding the road over Stevens Pass in 1949, completing its work in 1951. In the 1964 renumbering, the Primary State Highway numbers were dropped, leaving only US 2 (and US 195 east of Spokane) on the highway. The Monroe-Bothell branch became SR 202, and then SR 522.)