According to a 2008 oral history of the cheesesteak by Philadelphia Magazine, the city's most famous sandwich was invented by Pat Olivieri in 1930, the same year he opened Pat's King of Steaks. Pat's biggest rival is Geno's Steaks, which was founded in 1966.
Although there's lots of history between the two cheesesteak shops in South Philly, many people who live in the city will tell you to avoid Pat's and Geno's. From my experience, the lines are often long and there are other cheesesteak restaurants that offer great value and taste in the city. Still, there are some people that are loyal to these two cheesesteak restaurants.