In 1807, an Irish ship's surgeon recognized a slave at a Mississippi produce market as the son of an African king who had saved his life many years earlier. "The Prince," as he had become known to local Natchez, Mississippi, residents, had been captured by warring tribesmen when he was 26 years old, sold to slavetraders, and shipped to America. An educated, aristocratic slave, Abd Rahman Ibrahima was made overseer of the large cotton and tobacco plantation...