Lou Groen created McDonald’s Filet-O-Fish sandwich for restaurants in Catholic communities.
Groen operated a McDonald’s franchise in Cincinnati, Ohio, where many customers observed the Catholic practice of avoiding meat on Fridays. Sales fell sharply on those days, leading him to develop a fish sandwich as an alternative to hamburgers.
Ray Kroc initially viewed the product as a test against another proposed meatless sandwich, but the Filet-O-Fish performed strongly. It was added to the national menu in 1963 and became one of McDonald’s most enduring branded menu items.
The sandwich’s name refers to its fish filling, but the important branding story is its connection to a specific local customer need. It was not originally created as a general seafood product line.