The Big Mac was introduced by McDonald's in 1968 and became a major part of the chain's brand identity.
The sandwich was created by Jim Delligatti, a McDonald's franchisee in the Pittsburgh area. It used two beef patties, a middle slice of bread, lettuce, cheese, pickles, onions, and a special sauce. Its distinctive three-part bun helped separate it from ordinary hamburgers.
McDonald's promoted the Big Mac as a signature menu item, and its name became widely recognized outside the restaurant business. The sandwich later inspired the Big Mac Index, an informal economic comparison based on its price in different countries.
The Quarter Pounder was introduced earlier, in 1971, and the Filet-O-Fish dates to 1963. The McChicken was introduced much later, so none of those products matches the 1968 milestone.