The Siskiyou Trail was an early trading route used by native people and early trappers between the Willamette Valley and California. The trail was re-purposed as a settler’s route in 1846 following the creation of the Applegate Trail. The Pacific Highway was completed in 1992 following the trail route. Over time the Pacific Highway was upgraded and renamed to U.S. Highway 99 (US-99). In the 1950s, US-99 was further upgraded to freeway standards and renamed to Interstate 5 (I-5). The last Oregon segment of I-5 was the Marquam Bridge which was completed in 1966.
