In 1921, the McNally family opened a quick lunch at the highest peak of Chestnut Hill to serve hungry trolley operators.
But it was a happy mistake between two buns that put them on the sandwich map. Layer upon layer of specially stacked goodness that has made their creation famous far beyond Philadelphia.
"Actually the whole thing was a mistake," says Hugh McNally. "Without thinking I threw the onions on, the tomatoes on."
A warm Kaiser roll with melted cheese waits to wrap itself around a strategic stack of fresh roast beef, sauteed onions, Jersey tomatoes and salami.
"Right at the end we flip it back over because we want that salami to be blackened," explains Hugh's daughter Meg, who tops it off with a slather of secret sauce.
They call it The Schmitter, a nod to Schmidt's, the local beer regulars washed it down within their personalized pewter mugs that hang from the ceiling and line the walls.
Each one has a name and number etched onto the side along with the McNally family crest.
The story behind the green door and the hard-to-find sign started when Meg's great grandmother, Rose McNally, opened a quick lunch in 1921.
"Her husband Hugh drove the trolley," Meg explains. "When he would come to the end of the line there was nothing out here, nowhere to get a cup of coffee. She made the soups and the sandwiches."
That's what sisters Meg and Anne do today.
The Dickens has fresh turkey, stuffing and cranberry sauce. The GBS, George Bernard Shaw, is an ode to dad Hugh's favorite vegetarian author. It has a mixture of cheese, onions, peppers and Schmitter sauce.
By the way, The Schmitter has been served at Super Bowls, and local sports fans can now enjoy the Big League sandwich at Citizens Bank Park and Lincoln Financial Field.