The Lenten favorite was an answer to the problem of poor Friday sales.
According to an account in Reader’s Digest, when Cincinnati McDonald’s franchise owner Lou Groen noticed that his heavily Catholic clientele was avoiding his restaurant on Fridays, he suggested to McDonald’s owner Ray Kroc that they add introduce a fish sandwich.
Kroc thought fried fish wouldn’t fly, but suggested offering customers the choice of a meat-free “Hula Burger” made of pineapple and cheese on a bun and Groen’s Filet-o-Fish. Whichever sandwich was more popular would earn a spot on the menu.
Needless to say, the fish sandwich won, and Groen’s restaurant thrived. Since then, the sandwich has been McDonald’s fixture, all year long.