Dressing is important in Crab Louis (or, if you wish, Louie). It is mayonnaise, cream, lemon juice, and red chili sauce, usually with green onions and spice. But of course, what matters more is the crab. Fresh Dungeness crab makes all the difference. No one knows for sure where the Louis formula was created, or by whom, but food historians generally agree that the genesis of the “King of Salads” was sometime early in the 20th century, in either San Francisco or Seattle. And while it is available in restaurants all around the country, it is at its best in the Pacific Northwest.