Interstate 5 is the primary north–south route on the West Coast of the United States, stretching over 1,380 miles from the Mexican border in San Ysidro, California, to the Canadian border in Blaine, Washington. It is the only continuous Interstate to connect Mexico to Canada and serves as a vital transportation spine for the states of California, Oregon, and Washington. As a core part of the Interstate Highway System, I-5 links major cities including San Diego, Los Angeles, Sacramento, Portland, and Seattle.

In California, I-5 travels through a wide array of landscapes—coastal urban areas, Central Valley farmland, and the rugged Tehachapi and Siskiyou mountain ranges. It is notably straight and flat through much of the Central Valley, making it a preferred corridor for commercial trucking and long-distance travelers. In Oregon, the route threads through the Willamette Valley, home to the state’s largest cities and fertile agricultural regions. Washington’s portion of I-5 passes through major metros like Olympia, Tacoma, and Seattle before ending at the Peace Arch Border Crossing into British Columbia.

I-5 plays a critical role in freight movement, commuter traffic, and tourism across the Pacific states. It’s often cited for congestion challenges in urban stretches, particularly in Los Angeles and Seattle, where expansions and high-occupancy vehicle (HOV) lanes have been added. Despite its age and heavy use, I-5 remains a crucial economic and cultural artery, helping bind the West Coast together with one continuous route.