In 1775, after a decade of colonial protest over parliamentary taxation, Samuel Johnson famously complained, “How is it that we hear the loudest yelps for liberty among the drivers of negroes?” It was a good question and one that has dogged Americans ever since. That strident demands for freedom and equal rights under law came from a place where slavery was interwoven with everyday life, both North and South, has been called the central paradox of American history. As the dean of American historians, Edmund S. Morgan, wrote in the introduction to his own effort to unravel the problem, American Slavery, American Freedom (1975), “The paradox is American, and it behooves Americans to understand it if they would understand themselves.”

That chattel slavery contributed to the formation of the world’s longest-lasting republic is both true and almost beyond modern comprehension. In 1790, the nation’s first census counted nearly 700,000 slaves, almost 18 percent of the entire population. In the South’s most populous state, nearly four out of ten Virginians were slaves. And, despite fitful misgivings about the contradiction between ideals and practice, the slave population continued to grow over the next sixty years. On the eve of the Civil War, it had reached almost four million. Of the first seven American presidents, only John Adams and his son, John Quincy Adams, did not own slaves. When white Americans passionately attacked political oppression as “slavery,” it was more than a mere figure of speech; they knew exactly what slavery