What was McDonald's first product advertised as a breakfast sandwich?

The Egg McMuffin was McDonald’s first product advertised as a breakfast sandwich.

Herb Peterson, a McDonald’s franchise owner in Santa Barbara, California, developed the sandwich in the early 1970s. It used an English muffin, a fried egg, Canadian bacon, and cheese, with the ingredients assembled in a format that resembled an eggs Benedict adapted for quick service.

McDonald’s tested the Egg McMuffin before expanding it nationally in 1975. The item helped establish breakfast as a major part of the company’s daily business and created a durable association between McDonald’s and morning menu service.

The McGriddle and other breakfast products came much later. The Sausage McMuffin also belongs to McDonald’s breakfast history, but the Egg McMuffin is the product credited with launching the chain’s breakfast sandwich concept.