Judging by the ever-present lines at neighboring Pat’s and Geno’s—two historic rival institutions in a not-so-scenic stretch of the City of Brotherly Love—no sandwich arouses regional debate with quite as much intensity as the Philly cheesesteak. This seemingly simple sandwich of thinly-sliced ribeye, melted cheese (more on that in a minute), and optional vegetation (onions, peppers, mushrooms, etc.) has inspired not only fierce loyalties, but also its own particular rapid-fired patois as well. (“One whiz with” = One cheesesteak with Cheez Whiz and fried onions; “One provolone without” = One cheesesteak with provolone cheese without fried onions, etc.)

But where does this beloved sandwich come from? What stories lurk beneath its processed-cheese shell, nestled between layers of frizzled beef? Like so many iconic regional foods, the cheesesteak origin story has been conflated with myth and braggadocio so many times that it’s difficult to pin down a definitive truth. Even so, there are luckily a few key points that remain uncontested in the sandwich’s history.

To find out more, we spoke to Carolyn Wyman, food writer, Philadelphia food tour guide, and author of The Great Philly Cheesesteak Book, a veritable font of information on the history and evolution of the sandwich. In the process, we learned how the humble creation rose to prominence out of the Depression Era at the hands of its savvy inventor-come-marketer, and eventually grew into the icon it’s considered today.

Here’s an illustrated history of the evolution of the Philadelphia cheesesteak.

The Pre-Sandwich Era

Illustration by Louie Chin

Philadelphia’s Italian population (along with myriad other immigrant groups) boomed between 1870-1930, as political upheaval in the homeland encouraged many Italians to emigrate to America. Families from Abruzzi, Calabria, Sicily, and more joined Philadelphia’s already-established Ligurian population, settling largely in South Philadelphia.

Here, street vendors sold cheap sandwiches out of carts, using inexpensive cuts of meat like tripe, or, in some cases, just meat drippings, sans actual meat. These meals were meant as quick, easy sustenance for the neighborhood’s working-class clientele, and among their peddlers was the son of an Abruzzi government worker who left Italy as Mussolini rose to power. This son would soon invent a sandwich that would change the city forever.

A Chance Encounter With a New Creation

Illustration by Louie Chin

In 1930, the aforementioned son, Pat Olivieri, and his brother Harry were operating a food cart at the corners of 9th Street, Wharton Street, and Passyunk Avenue that dealt primarily in hot dogs and fish cakes. One day in 1933, Pat, bored of eating his own limited menu, implored Harry to visit a nearby butcher and come back with some beef that they could quickly cook up on at their stand for lunch. Harry returned with thinly-sliced ribeye, Pat “frizzled” it up with some onions on the flattop, and crammed it into a bun: voila, version 1.0 of the cheesesteak has arrived.

As legend has it, on that very day, the intoxicating perfume of beef and onions attracted the attention of a regular customer, a cabbie, who requested this brand-new, off-menu item for himself. The cabbie promptly advised the Olivieri brothers to focus on their new steak sandwich in lieu of fish cakes, and word of mouth about this delicious and previously unknown creation quickly spread. 

A Star Is Born

Illustration by Louie Chin

By 1940, Pat and Harry had saved enough money to turn their cart into a brick-and-mortar restaurant at the same corner, which they called Pat’s King of Steaks (though, it should be noted: you can still get a hot dog there). The earliest versions of the Pat’s sandwich involved only thin-sliced beef and onions, served on a crusty Italian loaf from a nearby bakery (a step up from the hotdog buns of version 1.0). Wyman points out that signage at the city’s oldest vendors still reads “steak shop,” as opposed to “cheesesteak,” owing to the decade-plus that the sandwiches were served lactose-free.

But it was really Olivieri’s marketing techniques that helped launch the cheesesteak from regional specialty to national icon. “The reason the cheesesteak really blossomed was because of Pat himself,” says Wyman. “He was a larger-than-life figure who visited local theaters and concert halls, bringing steak sandwiches to the stars, then luring them back to his shop and taking pictures of them eating. He spread the word about his sandwich all over the world via these celebrities, and made into a star.”

Rivlary (And Cheese) Emerge

Illustration by Louie Chin

A good story has drama to propel it, and the history of the cheesesteak is no different. Two major milestones must be noted on this front, though only one of them has a definitive date, while the other is shrouded in mystery and myth.  

In 1966, Joey Vento opened Geno’s Steaks mere feet from Pat’s King of Steaks, serving a near-identical menu, 24 hours a day (Pat’s is also open 24/7). Although hundreds of steak sandwich shops have opened across Philadelphia since Pat’s debut, the proximity of Geno’s and the corresponding media attention have fueled a rivalry for generations, with owners on both sides publicly denigrating the other’s business.

At this point, you’re likely wondering about the advent of cheese as it relates to its namesake sandwich. This particular topic is subject to some debate, but here is what we know: The earliest iterations of the steak sandwich involved steak and onions only, served on a chewy Italian loaf. One story has it that “Cocky” Joe Lorenzo, who worked at Pat’s in the 1940s, added provolone cheese to his own personal sandwich, thus inventing the cheesesteak as we know it today. However, Joey Vento of Gene’s also claims to have been the first to add cheese to his sandwiches, which would date the cheesesteak to the mid-‘60s. And this is to say nothing of Cheez Wiz, the processed cheese product that debuted in 1952 and quickly found its way onto sandwiches at Pat’s and beyond. Wyman, for her part, sides with the Joe Lorenzo version of the story.

Rise of the Alt-Cheesesteak

Illustration by Louie Chin

As cheesesteaks evolved from novelty to mainstream to icon, a market emerged for alternative “cheesesteaks” that could appeal to audiences who avoided steak and cheese for dietary or health reasons. In the early 1980s, a fellow by the name of Bill Schultz began selling chicken cheesesteaks to appease his calorie-conscious customers at his (now-closed) shop near University of Pennsylvania. More recently, vegetarian and vegan versions of the sandwich have appeared thanks to suppliers like Vegadelphia, which launched in 2004 selling plant-based versions of beef and chicken for sandwiches—proof that the City of Brotherly Love has room in its heart for cheesesteaks of every color and creed.