Interstate 5 - History

History

An extensive section of this highway (over 600 miles (970 km)), from approximately Stockton, California, to Portland, Oregon, follows very closely the track of the Siskiyou Trail. This trail was based on an ancient network of Native American footpaths connecting the Pacific Northwest with California's Central Valley. By the 1820s, trappers from the Hudson's Bay Company were the first non-Native Americans to use the route of today's I-5 to move between today's Washington State and California. During the second half of the 19th century, mule trains, stagecoaches, and the Central Pacific railroad also followed the route of the Siskiyou Trail. By the early 20th century, pioneering automobile roads were built along the path of the Siskiyou Trail, notably the Pacific Highway. The Pacific Highway ran from British Columbia to San Diego, California, and was the immediate predecessor of much of U.S. Route 99. The route of U.S. 99 was in turn used as a basis for much of the route of today's I-5.

A major deviation from the old U.S. 99 route is the Westside Freeway portion of I-5 in California's Central Valley. To provide a faster and more direct north-south route through the state, the decision was made to build a new freeway to the west and bypass Fresno, Bakersfield, and the rest of population centers in the area instead of upgrading the existing highway (which was re-designated as part of California State Route 99).