McDonald's Filet-O-Fish was invented by a franchisee fighting a pineapple burger

In 1962, Lou Groen, a McDonald's franchise owner in the Monfort Heights neighbourhood of Cincinnati, Ohio, faced a problem that affected Catholic-majority neighbourhoods across America: his restaurant was nearly empty every Friday. At the time, Catholic doctrine required abstaining from meat on Fridays, and McDonald's had nothing to offer but hamburgers. Groen was losing a fifth of his weekly revenue.

Groen experimented with a fish sandwich — a fried halibut fillet with a slice of cheese and tartar sauce on a steamed bun, priced at 29 cents. The goal was to match the McDonald's experience: fast, affordable, and familiar. The sandwich was a hit with his local customers. Groen took it to McDonald's corporate headquarters in Oak Brook, Illinois, hoping to add it to the national menu.

Ray Kroc, McDonald's founder, had his own idea: the Hula Burger — a grilled slice of pineapple with two slices of cheese on a cold bun. Kroc saw no reason to add fish to a hamburger chain. To settle the dispute, Kroc made a bet with Groen: on a Friday, both sandwiches would be sold at Groen's restaurant. The one that sold more would be added to the menu. The Filet-O-Fish won hands down.

McDonald's added the Filet-O-Fish to its national menu in 1965. It was the first non-hamburger item in the chain's history. By 2023, McDonald's was selling approximately 300 million Filet-O-Fish sandwiches annually worldwide. The Hula Burger was never seen again. A franchisee's local solution to a religious dietary restriction became one of the longest-running menu items in fast food.