The Simpsons are from one of these 3 states:
Well you tell me in what other state could the entire population be born with unnatural features, i.e. only 4 fingers on each hand.
Or they could be in Pennsylvania. Only Radioactive Man has five fingers. He was born with 4, but only after becoming radioactive did he gain an extra finger on each hand. Three Mile Island?
Unlikely to be Pennsylvania, so I will stick with one of the inbred southern states.