It has just been announced that a cache of previously unpublished letters by and to Benjamin Franklin has been discovered in London. It's a reminder that all sorts of things might be lurking out there in archives, filed under some obscure heading -- in this case, "Copies of Letters relating to the March of General Braddock."
It is also a reminder of how greatly historians depend on the self-promotional efforts of those they study. These letters survive because Franklin carried copies of them with him to London to impress people he might meet with his importance: "see, I corresponded with the commander of British forces in North America!" Sometimes it is those who work hardest to leave a historical legacy who end up the most famous.