I-5

About I-5

Also known as West Coast Highway corridor.

From San Ysidro, CA (Mexico border) to Blaine, WA (Canada border)

Interstate 5 is the principal north-south freeway of the West Coast, running about 1,381 miles from the Mexican border at San Ysidro, California, to the Canadian border at Blaine, Washington. It passes through all three Pacific states and links most of their largest cities, including San Diego, Los Angeles, Sacramento, Portland, and Seattle. As the western spine of the Interstate system, it carries the bulk of long-distance passenger and freight traffic along the coast.

The route crosses a wide range of terrain. In California it runs through coastal Southern California, climbs over mountain passes, and traverses the long, flat agricultural floor of the San Joaquin and Sacramento valleys. In Oregon and Washington it follows the Willamette Valley and the Puget Sound lowlands, passing near major rivers and mountain backdrops before reaching the Canadian frontier.

Interstate 5 is unique among mainland Interstates in touching both the Mexican and Canadian borders, anchoring the system at its low odd-numbered western edge. Its many auxiliary routes serve the metropolitan areas of San Diego, Los Angeles, Sacramento, Portland, Tacoma, and Seattle, distributing traffic through dense urban cores and around their bypasses.

State-by-state mileage

State	Miles
California	796.5
Oregon	308.1
Washington	276.6
Total	1,381.2

History

Interstate 5 was designated in 1957 as part of the original Interstate plan, replacing and paralleling older highways such as U.S. Route 99 through much of California and the Pacific Northwest. Construction proceeded over many years, with the rural West Side alignment through California's Central Valley and the urban segments in the major cities completed in stages.

The corridor has been continually widened and rebuilt to handle growth, and its set of auxiliary routes has expanded over the decades to serve the West Coast metropolitan areas it connects.

Major cities and places

Notable features

• Tejon Pass (Grapevine)
• Siskiyou Summit

Did you know

• It is the only mainland Interstate to reach both the Mexican and Canadian borders.
• The Grapevine climb over Tejon Pass north of Los Angeles is one of its most demanding grades.
• Siskiyou Summit near the Oregon-California line is the highest point on the entire route.
• It serves as the primary freight spine of the Pacific states.
• Interstate 405 forms a complete loop with I-5 around downtown Portland.