It is a known fact that the California roll was invented in the 1970s at an LA restaurant called Tokyo Kaikan by a sushi chef who either (a) wished to make Japanese maki sushi (rolls) more appealing to American palates&mdashnamely, by replacing the raw fish part with crab, cucumber, and avocado&mdashor (b) ran out of toro, or fatty tuna, one day and substituted avocado, for its similarly creamy, oily texture. Perhaps it was a combination of both that led to the first California roll. Still, in any case, it was a runaway national hit and proved an ideal transition for many Americans into the world of proper sushiden. Here are a few places to try it.