How do you define "The Grapevine" ?

It's I-5 going over the "hill" between Castaic and Grapevine.

The only towns on the way are Gorman near the top of Tejon Pass, the Frazier Park exit taking you 2 miles west to Frazier Park, then the small settlement of Lebec..

A point of interest along the way is Ft. Tejon, which was the western terminus of the US Army's camel group that crossed the Mojave desert in the 1850s. Civil War re-enactments are seen there many weekends. There is also info about the Great Earthquake of 1857, as it sits astride the San Andreas Fault.

Accross the freeway lies Tejon Ranch, one of the largest and oldest cattle ranches in the US. It is not open to the public.

As already stated, The Grapevine is named for the wild grapes that grow at the bottom of the hill.

It's terminus is obviously the small town (Grapevine, CA) which is at the bottom of the hill. I've always considered Gorman the southern end of it. Some may way Lebec, but Gorman is pretty close to the top of the pass.

In the olden days, my father told us that the area was called "the grapevine" because the road was twisted like a grapevine. But, the locals tell me it is named the The Grapevine because of wild grapes that grow in the area..

Copestir is right, its the grapes, but being a No Cal native, I always saw it as the Final approach to LA county.