The sandwich was the first non-hamburger menu item brought in by new McDonald's company owner Ray Kroc. Kroc made a deal with Groen: they would sell two non-meat sandwiches on a Friday, Kroc's own Hula Burger (grilled pineapple with cheese on a cold bun) and the Filet-O-Fish, and whichever sold the most would be added to the permanent menu. The Filet-O-Fish "won hands down" and was added to menus throughout 1963 until reaching nationwide status in 1965.
