Sometimes called deep-dish or pan pizza, an excellent type of pizza originating in Chicago in the early 1940s. Now often misdescribed as "thick crust", the pizza generally has a thin or medium crust made of flour and cornmeal, upon which is laid a thick layer of cheese, with tomato sauce or crushed tomatoes on top. It is available all over the world, although the authenticity is questionable outside of Chicago.
Interestingly, many prominent Chicagoland pizzerias serve only thin pizza (i.e. not Chicago-style) which is also very popular if not moreso among Chicagoans. Some area pizza parlors offer both styles, apparently to cater to out-of-town rubes who want to try Chicago-style.
"I ate a Chicago-style pizza in London and my anus hasn't been right since."
"My grandfather ate Chicago-style pizza at Pizzeria Uno in 1945. He is dead now."