The iconic McDonald's burger with two all-beef patties is the Big Mac.
Created by McDonald's franchisee Jim Delligatti, the sandwich debuted in Uniontown, Pennsylvania, on April 22, 1967. It expanded to McDonald's restaurants across the United States in 1968 and became the chain's flagship hamburger. Its signature construction uses a three-part sesame-seed bun, two beef patties, cheese, lettuce, pickles, onions, and special sauce.
A famous 1974 advertising jingle helped cement the burger's identity by listing its ingredients: “two all-beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame-seed bun.” The Big Mac is sometimes confused with a basic double cheeseburger, but its middle bun layer and special sauce distinguish it.
The sandwich also inspired The Economist's Big Mac Index, which compares purchasing power and currency values using the price of the widely available burger.