You know the jingle. You can probably taste that signature sauce on your tongue just from sense memory. But what do you really know about the McDonald’s Big Mac? From its origins as the brainchild of a crafty franchisee to its role in helping economists observe global exchange rates, here are some beefy facts about this iconic burger.

1. The Big Mac was modeled off the signature sandwich at The Big Boy.

In 1967, franchise owner Jim Delligatti ran several McDonald’s franchises around the Pittsburgh area, but found the fast food joint’s standard burger didn’t satisfy the hard-working blue-collar crews nearby. Rival burger chain, the Big Boy, offered a beefier sandwich with two patties, a twice-sliced sesame seed bun, lettuce, sauce, and cheese. So Delligatti adapted the recipe, adding pickles, onions, and making his own spin on the sauce. “This wasn’t like discovering the lightbulb,” he was quoted in John F. Love’s book, McDonald’s Behind The Arches.“The bulb was already there. All I did was screw it in the socket.”

2. The Big Mac became a big deal very fast.

Originally called “The Big Mc,” Delligatti’s creation was first sold in his hometown of Uniontown, Pennsylvania, for 45 cents. (Adjusted for inflation, that’d be about $3.56 today.) The burger was such a hit that it caught the attention of McDonald’s CEO Ray Kroc, who made it a nationwide menu item in 1968. The towering burger became a fast favorite, making up 19 percent of all total sales in 1969. By the signature sandwich’s 25th anniversary in 1993, 14 billion Big Macs had been sold. In 2020, the Big Mac was available in 200 countries worldwide; estimates suggest that 900 million are sold annually around the globe, with 2.4 million being bought every day.

3. The Big Mac was nearly called “The Aristocrat.”

Unsatisfied by the “Big Mc” name, McDonald’s executives were tossing around flashier possibilities, like “The Aristocrat” and “Blue Ribbon Burger.” Fast food history was made when 21-year-old secretary Esther Glickstein Rose weighed in with her suggestion: The Big Mac. For decades, it was assumed Delligatti or some Mickey D’s bigwig came up with the name. But in 1985, while commemorating the fast-food chain’s 30th anniversary, McDonald’s recognized Rose’s contribution, honoring her with public credit and a plaque that featured etchings of the Big Mac and the McDonald’s iconic Golden Arches.

4. The Big Mac’s special sauce has changed over the decades.

Once the Big Mac went national, the McDonald’s corporation began fine-tuning the recipe, testing two versions of special sauce in its chains. In 1972, the victor was declared and dubbed “Big Mac Sauce recipe ‘72.’” Nicknamed “special sauce” in a 1974 ad campaign, this ’72 sauce was the standard until McDonald’s tweaked the recipe in 1991 (possibly to cut costs). This revamp of the sauce ultimately went the way of New Coke, and in 2004, McDonald’s CEO Fred Turner ordered a return to the classic formula.

5. The secrets of the Big Mac’s special sauce were revealed after 45 years.

Many have speculated over the years that the Big Mac sauce is nothing more than regular Thousand Island salad dressing, but the recipe remained mysterious through all its incarnations—until 2012, when McDonald’s then-executive chef Dan Coudreaut prepared Big Mac Sauce on a Youtube video, revealing the ingredients to be mayonnaise, sweet pickle relish, yellow mustard, white wine vinegar, garlic powder, onion powder, and paprika. So, yeah, it’s pretty similar to Thousand Island dressing.

6. Bottled Big Mac Sauce has sold for thousands on eBay.

Even with the secret out, selling the original sauce proved powerful. McDonald’s occasionally puts bottles of the sauce up for sale, with proceeds going to Ronald McDonald House Charities. In February 2015, the very first bottle (of a limited run of 200) was auctioned off on eBay and sold for over $15,000 USD. When the charity auction was repeated the following year on eBay UK, the highest bid was $100,000. While that bid was ultimately dubbed a hoax, runner-up bids ran to an excess of $69,000 USD.

7. There are different Big Macs around the world.

The classic Big Mac recipe sticks to the ’74 jingle: two all-beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed (twice-sliced) bun. But McDonald’s offers a bevy of variations around the globe. In India, the beef patties were first swapped out with lamb, then later a chicken patty to create the Maharaja Mac. In Israel, a Kosher version of the Big Mac is offered without cheese. For a limited time in Japan, the second patty could be swapped for a tomato or a grilled egg.

The Mega Mac, available in several nations, offers a bigger patty and a second slice of cheese, while the Son of Mac (a.k.a. Mini Mac or Baby Mac) boasted one patty and no center bun slice. In 2016, McDonald’s swapped out the standard special sauce for a spicier blend with its Sriracha Big Mac, which has since been discontinued.

8. The Big Mac became a form of economic measurement.

Learn about currency exchange rates for just 563 calories.Yu Chun Christopher Wong/S3studio/Getty Images

In 1986, The Economist created the “Big Mac Index” to compare currency exchange rates between countries. Because the burger was so widely available, it offered economists a simple way to essentially compare apples to apples (or burgers to burgers). “Burgernomics was never intended as a precise gauge of currency misalignment, merely a tool to make exchange-rate theory more digestible,” The Economist reflected in 2021. “Yet the Big Mac index has become a global standard, included in several economic textbooks and the subject of dozens of academic studies.”

9. There’s a Big Mac museum in Pennsylvania.

Forty miles south of where the first Big Mc was served, the Delligatti family built a monument to their contribution to McDonald’s worldwide dominance. On August 23, 2007, the Big Mac Museum Restaurant opened in their North Huntington, Pennsylvania, franchise. The working fast food joint boasts displays like a wall-mounted timeline of the history of the Big Mac, a life-size bust of Delligatti, a bobblehead of lesser-known McDonald’s mascot Officer Big Mac, vintage packaging, and a display commemorating September 25, 1992, when Pittsburgh mayor Sophie Masloff ceremonially renamed the Pennsylvanian metropolis as “Big Mac USA” for the day. However, the main attraction is a 14-by-12-foot-tall Big Mac statue, picture-perfect for snapping memento photos.