When I was about to enter first grade, our family moved from Spokane, WA, to southern California, landing in the new Sunset Hills development on the outskirts of Thousand Oaks. We're talking late 60s/early 70s. That's where I first got bitten by the hiking/adventure bug, because there were all those hills and rocks to climb behind our home. Very much like the Chatsworth area you mention. From the edge of our development, you could look down into what my childhood memory recalls as a vast, sprawling canyon or valley (I'm sure it was not nearly as big as I remember). My dad always said it was Joel McCrea's ranch, and he told me how Joel was some sort of retired cowboy movie actor. Never did see anybody riding horses or firing off their revolvers, but maybe when I wasn't looking...