Interstate 5 (I-5) is a major north–south route of the Interstate Highway System in the United States, stretching from the Mexican border at the San Ysidro crossing to the Canadian border near Blaine, Washington. The segment of I-5 in California runs across the length of the state from San Ysidro to the Oregon state line south of the Medford-Ashland metropolitan area. It is the longest interstate in California, and accounts for more than half of I-5's total length. It is the more important and most-used of the two major north–south routes on the Pacific Coast, the other being U.S. Route 101 (US 101), which is primarily coastal. I-5 links the major California cities of San Diego, Santa Ana, Los Angeles, Stockton, Sacramento, and Redding. The San Francisco Bay Area is about west of the highway. I-5 is known colloquially as "the 5" to Southern California residents and "5" to Northern California residents due to varieties in California English. I-5 also has several named portions: the John J. Montgomery Freeway, San Diego Freeway, Santa Ana Freeway, Golden State Freeway, and West Side Freeway. Route description I-5 is part of the California Freeway and Expressway System, and is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. The segment of I-5 from State Route 89 (SR 89) to US 97 forms part of the Volcanic Legacy Scenic Byway, an All-American Road. I-5 is also eligible to be included in the State Scenic Highway System; however, it is a scenic highway as designated by the California Department of Transportation (Caltrans) only from SR 152 to I-580. San Diego County I-5 begins at the San Ysidro Port of Entry from Mexico in the San Ysidro neighborhood of San Diego. Immediately after the border, I-805 splits off to the northeast and serves as a bypass of I-5 that avoids Downtown San Diego. I-5 itself continues northwest and meets the western end of SR 905, a route that connects with the Otay Mesa border crossing. I-5 then continues northward and joins the southern end of SR 75, a highway connecting to Coronado via the Silver Strand. I-5 then enters Chula Vista, briefly leaving the San Diego city limits. It continues along the east side of San Diego Bay where it intersects with SR 54 and enters National City. From