The primary ingredient of a Caesar salad is romaine lettuce. This crisp lettuce serves as the base for the salad and is usually complemented by ingredients like croutons, Parmesan cheese, and Caesar dressing, which typically includes olive oil, garlic, anchovies, Worcestershire sauce, lemon juice, and egg. The Caesar salad was invented in the 1920s by Italian immigrant Caesar Cardini in Mexico and has since become a popular dish worldwide. It is often served as a starter or side dish and is beloved for its savory, tangy flavors.