The image is terrible and familiar. A man sits, his face in profile, his torso exposed. His back is a breathtaking mass of scars, crisscrossing his body and baring the brutality of American slavery. Reproduced as a carte de visite, the image circulated widely throughout abolitionist networks and was featured in Harper's Weekly. Its undeniable power testified to the evils of slavery. But who was this man and how did this image come to be? Bruce...