Jay, the only thing that comes to mind is Calico, CA. It's one of those sorta touristy places, a restored/rebuilt silver mining town. We enjoyed taking the mine tour and hearing about the history of the town, there's quite a bit to see and do. There may be other places as well, but when we lived in California, we spent most available time headed out to Arizona. Here's some info and a map. It's pretty easy to get to from Ontario but I'm not sure it would fit in with your time restrictions.