Three defining components separate this deep-dish style from the rest:
1. Sicilian-style dough
New York's dough is chewy, Chicago's is “biscuity”, and the Neapolitan style is ultra-thin and crispy. Detroit dough, however, most closely resembles Sicilian sfincione, a light and spongy focaccia of sorts.
2. Brick cheese bottom, tomato sauce on top
Detroit-style pizza makers load mild Wisconsin brick cheese directly onto the dough. This kind of cheese, which tastes similar to Havarti, has roughly double the amount of fat as mozzarella, so when it melts, a crunchy, buttery “frico” crust develops. Some places double-down on the fatty flavor by brushing their crusts with actual butter, but it's not required. The sauce then gets spooned over that delicious crust. Think of it as an inverted pizza.
3. Industrial pans
Born from repurposed industrial blue steel auto-factories in Detroit, the specialized seasoned pizza pan is responsible for the square (or now more rectangular) shape and the height and crispiness of the crust. Today Detroit-style pizza makers still swear by them. Find them here if you're interested in buying one of your own, though they're not necessary for my homemade version. More on that below.