The Egg McMuffin became McDonald's first nationally marketed breakfast sandwich.
Herb Peterson created the sandwich in the early 1970s at a McDonald's franchise in Santa Barbara, California. It combined a fried egg, Canadian bacon, and cheese on a toasted English muffin, giving customers a portable breakfast built around familiar ingredients.
McDonald's tested the item before expanding it across the United States. The Egg McMuffin helped establish breakfast as a major part of the chain's identity and gave McDonald's a signature product outside its traditional lunch and dinner menu.
The item is sometimes described simply as McDonald's first breakfast product, but that wording is broader than the documented claim. McDonald's had tested other breakfast foods; the Egg McMuffin is specifically notable as the breakthrough breakfast sandwich that was rolled out nationally.