In the 1940s, Pizzeria Uno in Chicago developed the deep-dish pizza, which has a deep crust that lines a deep dish, similar to a large metal cake or pie pan. Though the entire pizza is quite thick, the crust itself is only of thin to medium thickness, and the pizza has a very thick large layer of toppings. Because the pizza is so thick, it requires a long baking time and, if cheese was added on top, as is usual with most pizzas, the cheese would burn.
So, in a deep dish pizza, the toppings are usually assembled "upside down" with cheese, vegetables, and meats placed on top of the crust, and an uncooked tomato sauce on the top layer, to help the vegetables and meats cook all the way through in the oven.
In the mid 1970s, Chicago restaurants Nancy's Pizza and Giordano's Pizzeria developed a variant of the deep dish pizza, known as the stuffed pizza, which is even deeper and has a larger topping density than any other type of pizza. To keep the cheese and toppings contained, a thin layer of dough is added above the tomato sauce with a hole in the crust (similar to a pie) to let steam escape, and tomato sauce is added above the top crust.
4. Chicago Thin Crust