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. From San Ysidro, the segment of I-5 in California runs north across the length of the state, and crosses into Oregon south of the Medford-Ashland metropolitan area. 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 is known colloquially as "the 5" to Southern California residents, "5" to Northern California residents.