(CNN) – The fast food world is mourning the man who created the Big Mac.

Michael “Jim” Delligatti invented the iconic McDonald’s two-tiered burger at his franchise near Pittsburgh. He first introduced the seven-ingredient sandwich in 1967… after spending two years to come up with the right combo for it’s special sauce.

The burger — two all-beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun — was available nationwide the following year. Today, McDonald’s sells 900-million Big Macs a year worldwide. His family says the creator ate at least one Big Mac a week. Delligatti was 98-years-old.