Imo's Pizza is distinctive to St. Louis. Ex-St. Louisians swing by when they are in town. They pine away for the thin crispy cracker crust and orangey cheese. The crust and the cheese are what are distinctive. New to St. Louis transplants look at Imo's like that we are from Mars. And, the small square cut, orange color and super thin crust really are not found outside of St. Louis. Most newcomers don't get it. The sauce is slightly sweet, but other than that, nothing special. Imo's does enjoy a long relationship with local meat suppliers and uses quality, well seasoned meats.
Imo's uses Provel® Cheese. Provel is a proprietary blend of Swiss, Cheddar and provolone. You can buy it in some St. Louis grocery stores. You can read all about Provel on Wikipedia.
Imo's crusts are pre-made. You can buy the exact crusts next to the Provel in the store. Look for Roma Shells. "Shell" is a term for a pre-made pizza crust. Roma is owned by Imo's and makes the crusts for the stores as well as other pizzarias around St. Louis. The shells have been partially baked. They finish baking when the pizza is baked. They arrive in the store in pre-cut circles. This recipe should approximate an Imo's crust if you want to make one at home without buying the shells. Note: I have not tried the recipe, but after reading several, feel this should be the closest for people who do not have the facilities to cook long sheets of pizza crust and cut out 16" circles.
"Game Piece" Pizza sells more than 100,000 pizzas a day in all 50 states and more than 50 other countries. There are a few pockets where they have problems. Two of those pockets are Chicago and St. Louis.
Chicago has more than 800 single store (Mom & Pop's in the restaurant industry) locations. The Chicago tradition is you call in your order, it takes an hour to bake, and you pick it up. Once you have tried Gino's, you can understand why Pizza Hut and Domino's deep dish is just bread. Having a pizza delivered in 30 minutes is pretty meaningless when you want to go pick it up in an hour.
"Game Piece" Pizza spent a long time studying the St. Louis pizza market. They would have done a better job had they not spelled Imo's Eemo's. (True story. I should have kept a copy). Once they figured out who their competition was, they were able to get better results from their study. They discovered that most people will use a coupon and try other pizzas. They learned that people who considered themselves "Pizza Hut fans" or "Papa John's fans" switched around, especially if the price was right. Not Imo's fans. Most Imo's customers have only one type of pizza. Some will claim to have never bought any other pizza. It is hard to market to someone who will not taste your food and does not care about the price.
This led to the "Game Piece" Pizza thin crust. the thin crust was developed specifically for the St. Louis market. At first, "Game Piece" Pizza bought Roma shells from Imo's. The Imo's franchisees were so "pleased" that their boss was selling food to their competition, they threatened to sue. "Game Piece" Pizza reverse engineered the thin crust and now has someone else make it.
The founder/owner of "Game Piece" Pizza flew to St. Louis to try Imo's and his new crust before the tests went beyond the St. Louis area. Thin Crust and pseudo Provel is now available nation wide.