SR 9 winds through the mountains north of Santa Cruz, passing through the communities of Paradise Park, Felton, Ben Lomond, Brookdale, and Boulder Creek, where State Route 236 departs from SR 9 to provide access to Big Basin Redwoods State Park.

At the summit of the Santa Cruz mountains (the junction with SR 35 and after a steep climb), there is a vista point offering a (somewhat obstructed) view of the Bay Area.

[5] At Fruitvale Avenue in Saratoga, SR 9 briefly becomes a four-lane highway with a large center divider.

Over the years, SR 9 has been popular among car enthusiasts from all over Northern California and beyond looking to test their skills on the scenic winding highway.

The experience of driving the road's challenging curves has led to the local term "9burgring", named after the Nürburgring racetrack in Nürburg, Germany.

[19] Except for a short realignment in the mid-1950s onto Route 69 (now I-880 and SR 262) between Milpitas and Warm Springs,[20] this alignment remained until the 1964 renumbering.

[21] In 1964, SR 9 was moved to its present alignment, taking over the previously unsigned Route 42 from Saratoga to Los Gatos.

Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage.