The Hatfields and McCoys were a famous example of feuding families in the United States. The feud began during the Civil War as the Hatfields and the McCoys found themselves on opposing sides of a war. The Hatfields, living near the border of West Virginia, fought for the Confederacy. Meanwhile, the McCoys lived in Kentucky and were on the side of the Union. The first act of violence between the two families occurred when one of the McCoys was killed by a home-defense group, thought to have been run by one of the Hatfields.
Later animosity between the two families deepened over several scandals: a stolen pig, murdering a witness for a trial, a taboo romance (think Romeo and Juliet), rioting and a subsequent stabbing on an election day, vicious acts of retribution, and of course, shooting and killing each other. Violence escalated until people thought the state militia should be brought in.