The Filet-O-Fish became McDonald’s first nationally sold fish sandwich in 1963.
Franchisee Lou Groen developed the sandwich at a restaurant in Cincinnati, Ohio, where many customers observed meatless eating on Fridays. Sales were especially weak on that day, so Groen proposed a fish-based alternative that could attract customers without changing the restaurant’s basic service model.
The sandwich originally used a breaded fish fillet, tartar sauce, and cheese on a bun. It was tested against a competing meatless sandwich before McDonald’s adopted it nationally.
The Filet-O-Fish is often described simply as a seasonal religious response, but its importance was broader: it showed how regional franchisee ideas could become national McDonald’s products. The recipe and fish species have changed in different periods and markets.