Chicago, Illinois was once a playground for mobsters and corrupt politicians. It wouldn't be the third-largest city in the U.S. today if it weren't for the shady dealings that went on just beneath its streets.

New York City is the biggest city in the country, but it's got some dark secrets. Founded by covert groups, overrun with gangs and mob bosses, and ruled by secret societies, this is the true foundation of the city that never sleeps.