I grew up and still live in Philadelphia. I was discussing with my girlfriend about how one of the public parks/squares used to be a potter's field, and she cheerfully remarked that the bodies are probably still there, underneath the grass where people talk and relax. (Nobody knows because most people don't read the plaques.)
It reminded me of to that scene where Cole pointed out "they used to hang people here."
I just thought it was a funny coincidence.