TKAM and The Grey Ghost

On page 15 when Dill dared Jem to go up and touch the house and he'd swap him The Gray Ghost for doing it, I knew that he meant a marble.  

I assumed it was a marble because of my extensive Little House on the Prairie experience. As a kid growing up in the 70s, Little House on the Prairie was must-see tv. Those prairie kids played, swapped, and won/lost marbles with names like The Gray Ghost all the time, so when I read that, I felt like I "knew" what it was.

LO-AND-BEHOLD, it isn't a marble after all!

Do you know what The Gray Ghost is?

Click here to see if you are correct - and to learn a little about The Gray Ghost's influence on Harper Lee's novel.