Much of 'Blood Meridian' is based upon the murder of Indians in the American Southwest and Mexico by a gang of white outlaws who then sell the scalps of their victims. How common was this practice?

Came across this randomly. Here's some resources for you:

Much of what McCarthy wrote in Blood Meridian is historical. At least, it was written about in the past. Most of it is based on My Confession: Recollections of a Rogue written by Chamberlain who is in the novel. For example, when one of the Delawares brains 2 infants, I believe there was a historical description of someone smashing an infant on a rock. Judge Holden has some enigma to him as it seems Chamberlain is the only account of Holden. I believe we have handbills for Glanton, but no mention of the judge. But I could be wrong.