From 1501 to 1867 more than 12.5 million Africans were brought to the Americas in chains, and many millions died as a result of the slave trade. The US constitution set a 20-year time limit on US participation in the trade, and on January 1, 1808, it was abolished. And yet, despite the spread of abolitionism on both sides of the Atlantic, despite numerous laws and treaties passed to curb the slave trade, and despite the dispatch of naval squadrons to patrol the coasts of Africa and the Americas, the slave trade did not end in 1808. Fully 25 percent of all the enslaved Africans to arrive in...