Pat's King of Steaks, at 1237 East Passyunk Avenue at the south end of the Italian market and directly across the street from its main competitor, Geno's Steaks, was founded Pat and Harry Olivieri in 1930. The brothers are generally credited as the 1933 co-creators of the Philly Cheesesteak.
In 1933 the brothers were working their hot dog stand when they decided to try something different for lunch. Pat sent Harry to the market for some inexpensive steak. The brothers thinly sliced the steak, then grilled it along with some chopped onions. The aroma attracted a cabdriver who was a regular customer; he asked to try the dish which the brothers called a steak sandwich and sold to him the sandwich for ten cents. Soon after the brothers started selling steak sandwiches instead of hot dogs. By 1940, they had saved enough to rent space to open a restaurant at the same spot that they had their stand. The two brothers worked at the restaurant for 15 to 18 hours a day for the next few decades while the restaurant was open 24 hours a day. Harry worked at the Philadelphia Naval Yard during World War II before returning to the restaurant.
By the 1950's, there were other businesses in the area selling similar steak sandwiches. Geno's Steaks claimed they were the first to add cheese to the recipe, though Harry's son, Frank, claims he first added Cheese Whiz in the 1960's. After pulling back from expansion and franchising efforts in the 1980s, the business was divided up by the Olivieri family. Harry and his son kept the original location, today run by Harry's grandson, Frank Jr. Pat's son Herbert opened "Olivieri's Prince of Steaks", later to be the source of a family dispute.