Although the McDonalds brothers established their first restaurant in California in 1940, the legendary burger was launched into history only in 1967 by McDonald's franchisee Jim Delligatti in Uniontown, Pennsylvania. Seeing its popularity, a year later the chain put it on menus nationwide, and eventually around the world.
Known by the catch-phrase "two all-beef patties special sauce lettuce cheese pickles onions on a sesame-seed bun," the Big Mac sold back then for just 45 cents. Inflation has taken its toll, but it is still a deal today at, in the United States, 2.69 dollars.
"Forty years ago, I would never have dreamed that my creation would turn into a piece of Americana," said Delligatti, now 89.
For the occasion he is inaugurating a museum-cum-restaurant commemorating the sandwich -- with the four meters by 3.5 meters (14 feet by 12 feet) "world's largest" statue of a Big Mac -- in North Huntingdon, Pennsylvania, close to Pittsburgh.
"Adult customers at the time were looking for a sandwich made just for them. I gave them what they wanted and now I'm celebrating the anniversary of a true icon," he said.
Today, with 30,000 restaurants in more than 100 countries, McDonald's sells more than a half-billion Big Macs in the United States alone each year, and millions more in other markets -- especially in Japan, the second biggest market.
Its global omnipresence has made the Big Mac an economic icon. As a way of measuring relative cost of living in different countries, the Economist magazine created the Big Mac index, which compares the price of the sandwich in each market.
The price ranges from 1.45 dollars in China to 4.01 in Britain and a whopping 7.61 in Iceland, according to the magazine's most recent July tabulation.