Who created McDonald's Filet-O-Fish sandwich?

Lou Groen created McDonald's Filet-O-Fish sandwich.

Groen operated a McDonald's franchise in a heavily Catholic neighborhood of Cincinnati, Ohio. During Lent, when many Catholics traditionally avoided meat on Fridays, his restaurant faced a substantial drop in hamburger sales. He developed a fish sandwich to attract customers who wanted a meatless option.

The sandwich was tested against a competing meatless product associated with a pineapple-based topping. McDonald's selected Groen's fish sandwich, and the Filet-O-Fish was added to the national menu in 1963.

The product is sometimes incorrectly credited to Ray Kroc because Kroc led McDonald's expansion. Kroc supported the menu test, but Groen was the franchisee who developed the sandwich concept. Its tartar sauce, fish fillet, and cheese became its recognizable combination.