Here's yours truly with a reproduction of Quantrill's famous black flag the rebel guerrilla supposedly flew as a sign that he'd take no prisoners. It's in the Clay County Savings Association bank museum. This bank, of course, was the first target of the James gang. This photo was taken by Rex Dickson, who shows no patience whatsoever with my obsession with Missouri's Civil War, but has seen a lot of the sights anyway. I wrote about the Liberty bank as part of my Gadling series on our Jesse James road trip.
Quantrill was the baddest of a bad crew. His gang slaughtered civilians, scalped soldiers, and raised hell generally. Frank James rode with him during the Civil War, as did famous outlaw Cole Younger. Jesse James may have ridden with Quantrill too before joining Bloody Bill Anderson in his own group.
This is an interesting flag for several reasons. You'll notice that Quantrill's name is misspelled. During the war his name was generally spelled with an "e", and the bushwhacker leader didn't exactly have a strong motive for correcting people. It's debateable whether he actually had a flag like this, though. There are several references to Quantrill's black flag, but both Frank James and Cole Younger said there never was one. At the time, "raising the black flag" meant that you'd show no mercy, so perhaps Quantrill's flag was only metaphorical.