Imo's is the dominant local pizza chain — over 90 locations across the metro area — and the best-known purveyor of the regional St Louis-style pizza: a thin, cracker-like crust, sweet tomato sauce, and a smoked processed cheese blend called Provel that does not melt or stretch like mozzarella.
This is, fairly, the most controversial pizza in America. It is small, square-cut, and not what most visitors expect. But it has been a fixed point in the St Louis food landscape for generations and is genuinely good once you adjust expectations — sweet, smoky, salty in a way that goes well with cold beer. Order extra Provel if you want the full effect.