What is the rectangle

Know how every city has that one area which is notorious for what might be gently described as sinful activity? Well, in the town in this novel that area has a name: the Rectangle. In a story about almost a whole town trying to do what Jesus would do as an experiment in liberal Christianity, the Rectangle would be a natural battlefield between good and evil. And so it is, metaphorically speaking:

“The end of the week found the Rectangle struggling hard between two mighty opposing forces. The Holy Spirit was battling with all His supernatural strength against the saloon devil which had so long held a jealous grasp on its slaves.”