Interstate 605 is a 27-mile-long (43 km) major north–south auxiliary Interstate Highway in the Greater Los Angeles urban area of Southern California. It runs from I-405 and State Route 22 (SR 22) in Seal Beach in Orange County to I-210 just south of the Irwindale–Duarte border in Los Angeles County. The San Gabriel River Freeway closely parallels the San Gabriel River for most of its alignment, hence its name, which is one of the few Southern California freeways not named after a city along its route. But similar to other freeways in the area, I-605 is also known colloquially as "the 605" to Southern California residents (See also California English § Freeways).