In 1775, Thomas Jeremiah was one of fewer than five hundred "Free Negros" in South Carolina and, with an estimated worth of £1,000 (about $200,000 in today's dollars), possibly the richest person of African descent in British North America. A slaveowner himself, Jeremiah was falsely accused by whites--who resented his success as a Charleston harbor pilot--of sowing insurrection among slaves at the behest of the British. Though a free man, Jeremiah...