I live adjacent to a no-commercial zone city called La Habra Heights and the Puente Hills that have multiple hill climbs ranging from 1/4 - 2 miles.
There are dozens of variations that I can use ranging from 15 to 60 miles with 100+ feet of climb per mile. My "Go To" rides are right outside my door.
If I want something longer, I am a 20 minute drive to the foothills of the San Gabriel Mountains that offer Cat HC, 1 and 2 climbs.