Pizza originated in southern Italy, but it took on a life of its own here. America's first specimens were simple flatbreads that emerged from bakeries' coal-fired ovens with a fetching bituminous char.
America's pizza map is a crazy quilt of invention, from inspired to insane. If you doubt that, have a taste of pulled-pork pizza in Memphis, or saltine-thin, unleavened-crust pizza in St. Louis, where mozzarella is shunned in favor of Provel cheese, a mix of cheddar, Swiss, and provolone. Detroit's signature is a thick-crust variation, called square pizza because it is cut into squares, gilded with caramelized cheese, and dotted with sauce. In the pork-loving Quad Cities region of Illinois and Iowa, pizzas come blanketed with ground Italian sausage, and they are cut into long pieces called "strips." Square, lightly sauced Grandma pizza is a Long Island specialty. Similar pizzas are known in other parts of the country as bakery pizza; a whole isn't a pie, it's a tray.