Chicago, more specifically 'Pizzeria Uno", is said to be the birthplace of Deep Dish Pizza. City lore has it that a Texan named Ike Sewell created the dish at his bar and grill named Pizzeria Uno in 1943.
During the depression of the thirties, followed by the war years of the forties, Americans ate one-dish meals of "casseroles", easily procured ingredients that would satisfy the stomach, stretch the budget and not cost many ration coupons. Therefore, the more you could load onto a pizza crust, the better it would be, and doubtless a deep pan would be more like a casserole. Moreover, the crust would not need the fancy stretching and pushing, even tossing, that the traditional Italian thin pizza would require. The mozzarella cheese would be on the bottom and the crust and toppings would all bake and ooze together and become one of America's legacies to fast foods nationwide and waistwide!