The Question and Answer section for Outliers is a great resource to ask questions, find answers, and discuss the novel.
Harlan is a small town in Kentucky where a feud started between two families in the 1800's.
From the text:
All the outliers we've looked at so far were the beneficiaries of some kind of unusual opportunity. Lucky breaks don't seem like the exception with software billionaires and rock bands and star athletes. They seem like the rule.