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I-5

Interstate 5 (I-5) is a major Interstate Highway on the West Coast of the United States, serving as the region's primary north–south route which goes south all the way to the Mexican border at San Ysidro, California. It travels 277 miles (446 km) across the state of Washington, running from the Oregon state border at Vancouver (in Metro Portland), through the Puget Sound region, and to the Canadian border at Blaine. Within the Seattle metropolitan area, the freeway connects the cities of Tacoma, Seattle, and Everett. I-5 is nicknamed as the Purple Heart Trail for its entire length in Washington.

I-5 is the only Interstate to traverse the whole state from north to south and is Washington's busiest highway, with an average of 274,000 vehicles traveling on it through Downtown Seattle on a typical day. The segment in Downtown Seattle is also among the widest freeways in the United States, at 13 lanes, and includes a set of express lanes that reverse direction depending on time of the day. Most of the freeway is four lanes in rural areas and six to eight lanes in suburban areas, utilizing a set of high-occupancy vehicle (HOV) lanes in the latter. I-5 also has three related auxiliary Interstates in the state, I-205, I-405, I-605 (proposed) and I-705, as well as several designated business routes and state routes.

The freeway follows several historic railroads and wagon trails developed during American settlement of western Washington in the mid-to-late 19th century. The state legislature incorporated local roads into the Pacific Highway in 1913, connecting the state's southern and northern borders between Vancouver and Blaine. The Pacific Highway was built and paved over the next decade, and became the northernmost segment of the national U.S. Route 99 (US 99) in 1926.

The federal government endorsed the creation of a national expressway system in the 1940s, including several bypasses on US 99 that were built by the state in the early 1950s. The state's planned toll superhighway in the Seattle area was shelved in favor of a federally-funded freeway under the new Interstate Highway System, under which I-5 was created in 1957. Construction of I-5 was completed in 1969, and several segments of the highway have been widened or improved in the decades since.

Route description[]

Southwestern Washington[]

South Sound region[]

Seattle and Shoreline[]

Snohomish County[]

Skagit and Whatcom counties[]

Seattle express lanes[]

Express lane exit list[]

The entire highway is in Seattle, King County.

History[]

Early state and national highways[]

State upgrades and Interstate planning[]

Interstate construction[]

Seattle planning and construction[]

Major projects and incidents[]

Planned improvements[]

Exit list[]

See also[]

I-5 (CA)
Auxiliary routes of Interstate 5
I-5
California
I-5E (former) • I-5W (former) • I-105I-105 (former) • I-205I-305 (unsigned) • I-405I-505I-605I-705 (fictional) • I-805I-905 (future)
Oregon
I-105I-205I-305 (unbuilt) • I-405I-505 (unbuilt)
Washington
I-205I-405I-605 (unbuilt) • I-705
Business routes of Interstate 5
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