I don't recall a time when all gambling was banned in California. I think there may have always been card clubs. I think the rule was that any game that could be considered a game of "skill" (poker) was generally allowed but games of "chance" (dice) were forbidden. I would think that to identify the illegal clubs you would have to identify those that had more than just games of "skill". I can't speak with authority but I think that a lot of illegal gambling went on in the foothills of Northern California well up into the 50s. I talked to some people in Sonora who verified that Mack's Mountain Club had full up gambling in the back room including craps and slots. The city of Jackson was especially notorious for gambling and related sins - but I think it was not uncommon all along Highway 49 that runs down through the old gold mining areas of California. I'm sure there were plenty of upscale clubs in San Francisco as well but I don't know anything about them.

Chas