As I was writing, I wished more than once for a photo, which I always find a catalyst for writing. I didn't have a powerful visual image of him in my mind at first. I found myself wishing even harder for images of his wife, Rebecca, and his parents and children, who are all somewhat shadowy in the historical record. They eventually took shape for me with only a few throwaway descriptions to go on--Rebecca was black-haired and more than commonly tall, for instance.
Looking at photos of Victorian descendants, all lined up with their many children, was helpful. And a photograph of Boone's last son, Nathan, exists. He's supposed to have looked like his father. It's strange to look at his face, and to see how his eyes slide away from the viewer, refusing to be seen quite head-on.