Slavery, the argument goes, was an inefficient system. The use of enslaved labor has been presented as premodern, a practice that had no ties to the capitalism that allowed America to become a leading global economy. This is untrue. Slavery, particularly the cotton slavery that existed from the end of the 18th century to the beginning of the Civil War, was a thoroughly modern business, one that was continuously changing to maximize profits.
(People who applaud the achievements of economic growth tend to omit the fact it was achieved off the back of exploitation like this)