Almost all the ingredients in this sandwich, especially the sprouts and avocado, are associated with the health craze of the 1960s and '70s in California. It isn't so much that a Californian created this recipe, but rather that the combination has come to be synonymous with California cuisine. Multigrain bread is part of that trend, and so-called California sandwiches are often vegetarian, as in this version. You could also include slices of turkey with the cheese.