The Egg McMuffin gave McDonald's its first widely successful breakfast brand in 1971.
Herb Peterson, a McDonald's franchisee in Santa Barbara, California, created the sandwich with an English muffin, a poached egg, Canadian bacon, and cheese. Its format made breakfast portable and helped McDonald's enter a daypart that had not previously been central to its identity.
The Egg McMuffin was initially tested locally before expanding through the McDonald's system. Its name established the “Mc” naming pattern that became a powerful part of the chain's product branding.
The sandwich is sometimes dated to 1972 because that was the year of broader national introduction. The product itself was created and first sold in 1971, making that year the key origin date.