The original pans weren't pizza pans at all — Buddy's Pizzeria, which invented the style in 1946, baked the first square pies in blue-steel industrial parts trays borrowed from local auto factories.
A thick, airy dough is pressed into a square steel pan and topped with cheese all the way to the crust's edge, where it caramelizes into a crisp, lacy crust; tomato sauce is ladled in stripes on top after baking. Pizzerias sell it by the square slice for a quick lunch.
Philly Cheesesteak