Often, Angelenos refer to the 40-mile stretch from just north of Castaic to the bottom of the grade where the I-5 enters the San Joaquin Valley as “the Grapevine” (the orange and yellow portion of the I-5 in the map below). The stretch is almost as well known to Angelenos as the Hollywood Freeway (see Old Ridge Route). Actually, the Grapevine is only the six-mile portion between Fort Tejon and the bottom of the grade (the yellow portion of the I-5) to the north.
So why is it called "The Grapevine?"
In 1772, searching for a shorter pass between San Diego and Monterey, Acting Governor of Alta California Pedro Fages discovered a canyon pass that led to the Santa Clarita Valley. He named it "La Canada de Las Uvas" or “Canyon of the Grapes” because of an abundance of wild grapevines along the route. Although it proved to be an excellent pass, early travelers were forced to hack their way through thickets of wild grapevines. Today, you can still see wild grapes growing along the canyons that, at quick glance, easily resemble ivy.