Interstate 210 and State Route 210 (California)

Route 210, consisting of the contiguous segments of Interstate 210 (I-210) and State Route 210 (SR 210) forming the Foothill Freeway, is a major east—west state highway in the Greater Los Angeles area of the U.S. state of California. The western portion of the route is an auxiliary Interstate Highway, while the eastern portion is a state highway. The entire route was upgraded to Interstate Highway standards by 2007, and the California Department of Transportation (Caltrans) has requested permission to re-sign the eastern portion as an Interstate Highway.

The name Foothill Freeway is a reference to Foothill Boulevard and the San Gabriel Mountains, both of which run parallel to the freeway for most of its length. The freeway connects Los Angeles with its northern suburbs following the foothills of these mountains. The freeway runs from the Sylmar district of Los Angeles east to Redlands.

Currently all of the Foothill Freeway is designated Route 210. Historically, the Foothill Freeway spanned multiple numerical designations. Additionally, the I-210 designation has changed routings; previously including a portion of what is now the Orange Freeway (SR 57). East of Pasadena the Foothill Freeway parallels, and in some parts replaced, the route of former U.S. Route 66.