The Chicago crust is a different consistency. It's drier than New York style crust, and not as flexible. It's more like a dense bread. They line a cast iron skillet with the dough oozing up the sides, then layer in meat first, then cheese and other toppings, and finally put the sauce on top, locking it all in.
You are supposed to eat it with a knife and fork, so it really is more like a pizza flavored casserole. It's delicious and amazingly unhealthy.