Even if you don't know how their famous argument began, you've probably heard about the bad blood between the Hatfield family and the McCoys.
Devil Anse and Old Ran'l.
The Hatfield-McCoy feud (or McCoy-Hatfield feud, depending on which family you ask) dates back to 1863. The two families lived on either side of the Big Sandy River, with the Hatfields in West Virginia led by William Anderson "Devil Anse" Hatfield, and the McCoys in Kentucky led by "Old Ran'l" Randolph McCoy.
The families fell out after the death of Asa Harmon McCoy. Asa was one of the few men from either family who fought for the Union in the Civil War. He was murdered while traveling home from the war, and Devil Anse was the prime suspect. While he was later proven not guilty, the two families continued to feud for decades.
The Hatfields in 1897.
The feud was so bad it was dubbed a "war" by local newspapers, and both states threatened to send their militias to attack the other family. At least 13 family members or their supporters were killed between 1880 and 1891 alone.
Famously, a dispute over a pig owned by the McCoys and stolen by the Hatfields led to even more violence. Land disputes and revenge killings only made things worse. But almost 100 years after the feud began, the families came up with a creative way to settle their arguments once and for all.