The salad's creation is generally attributed to restaurateur Caesar Cardini, an Italian immigrant who operated restaurants in Mexico and the United States. Cardini was living in San Diego but also working in Tijuana where he avoided the restrictions of Prohibition. His daughter Rosa (1928–2003) recounted that her father invented the dish when a Fourth of July 1924 rush depleted the kitchen's supplies. Cardini made do with what he had, adding the dramatic flair of the table-side tossing "by the chef." A number of Cardini's staff have said that they invented the dish.
Julia Child said that she had eaten a Caesar salad at Cardini's restaurant when she was a child in the 1920s. The earliest contemporary documentation of Caesar Salad is from a 1946 Los Angeles restaurant menu, twenty years after the 1924 origin stated by the Cardinis.
Hotel Caesar's on Avenida Revolución, c. 2000
The original Caesar salad recipe (unlike his brother Alex's Aviator's salad) did not contain pieces of anchovy; the slight anchovy flavor comes from the Worcestershire sauce. Cardini was opposed to using anchovies in his salad.
In the 1970s, Cardini's daughter said that the original recipe included whole lettuce leaves, which were meant to be lifted by the stem and eaten with the fingers; coddled eggs; and Italian olive oil.
Bottled Caesar dressings are now sold by many companies.
The trademark brands, "Cardini's", "Caesar Cardini's" and "The Original Caesar Dressing" are all claimed to date to February 1950, though they were only registered decades later, and more than a dozen varieties of bottled Cardini's dressing are available today. Some recipes include mustard, avocado, tomato, bacon bits, garlic cloves or anchovies. Cardini's Brand original Caesar dressing is somewhat different from Rosa's version.
Many variations of the salad exist; for example, by topping a Caesar salad with grilled chicken, steak, or seafood. Certain Mexican restaurants may improvise on items such as substituting tortilla strips for croutons or Cotija cheese for the Parmesan. 
Ingredients according to the Hotel Caesar's recipe from about 2006:
There is inherent risk of infection by salmonella bacteria occasionally found in raw egg from cracked or improperly washed eggshells. This is a concern with many similar dressings that are emulsified with eggs, though generally the pH level is thought to be acidic enough to kill those bacteria. Nevertheless, later versions of the recipe call at least for briefly cooked coddled eggs or pasteurized eggs. Recipes may omit the egg and produce a "Caesar vinaigrette". Many variations of this salad exist; in fact, Yogurt is sometimes substituted for the eggs to maintain a creamy texture and others call for using mayonnaise, oil and vinegar.
^"Cesar Cardini, Creator of Salad, Dies at 60". Los Angeles Times. November 5, 1956. "Caesar Cardini, 60, credited with the invention of the Caesar salad, died [...]"|accessdate= requires |url= (help)
^"Rosa Cardini". Telegraph. September 21, 2003. Retrieved 2012-02-10. "Rosa Cardini, who has died in California aged 75, turned the salad dressing created by her father, Caesar, into a staple of modern dining and a million-dollar business. Although the origin of the Caesar Salad is a topic hotly debated by epicures, the generally accepted version is that it was first popularised in the United States in the late 1920s by an Italian immigrant, born Cesare Cardini. He and his brother Alessandro moved to San Diego from Milan after the Great War and then decided to open a restaurant just across the border in Tijuana, Mexico, to attract Americans frustrated by Prohibition."
^1998 notes on claims: "Paul Maggiora, a partner of the Cardini's, claimed to have tossed the first Caesar's salad in 1927 for American airmen from San Diego and called it "Aviator's Salad. Caesar's brother Alex had claimed to have developed the salad (he too allegedly called it "aviator's salad"). Livio Santini claimed he made the salad from a recipe of his mother, in the kitchen of Caesar's restaurant when he was 18 years old, in 1925, and that Caesar took the recipe from him.
^ abJulia Child, From Julia Child's Kitchen, 1975.
^"My father always used Lea and Perrins Worcestershire sauce, and anchovies are one of its ingredients. [...] He meant this to be a subtle salad, and anchovies can be overwhelming." (Above quoted 1987 interview with Rosa Cardini)
^United States Patent and Trademark Office, serial numbers 73426710 "Cardini's", registered 1983 by Caesar Cardini Foods, 73782270 "The Original Caesar Dressing" and "Caesar Cardini's", registered 1989 by Dolefam Corporation, which later merged with T. Marzetti, Search at http://tess2.uspto.gov
^Doral Chenoweth on this: "In my reviewing career I have found alleged Caesar salads in this country prepared with [...] [editor's note: almost anything]. It was there that I decided to take up the cause." "I walked from the border to Caesar's Bar & Grill, 5th and Main streets. The second floor ballroom was the salad restaurant. Two chefs were treating tourists to technique. They still use Cardini's preferred wooden bowls. My conversation with one of the chefs went like this:
Q - Where does the Romaine come from? A - Da states.
Q - Where does the grated Parmesan come from? A - Da states.
Q - Where do you get the eggs? A - From da chickens. Those answers were satisfying. I recrossed the border vowing to defend Caesar Cardini."