The Hatfields & the McCoys / Bruce Wexler.
(Book)

Bad blood between the Hatfield and McCoy families spiraled into the most infamous feud in American folklore. Their animosity simmered for over forty years and often flared into murderous violence. It led to over a dozen deaths, the destruction of property, orphaned children, and childless parents. Although it is estimated that there were only around thirty combatants on each side, this legendary vendetta cast a dark stain across the whole of Appalachia.