From the earliest settlements, inhabitants of the southern colonies had shared a great deal with northern colonists. Most whites in both sections were British and Protestant, spoke a common language, and celebrated their victorious revolution against British rule. The creation of the new nation under the Constitution in 1789 forged political ties that bound all Americans. The beginnings of a national economy fostered economic interdependence and communication across regional boundaries. White Americans everywhere praised the prosperous young nation, and they looked forward to its seemingly boundless future.

Despite these national similarities, Southerners and Northerners grew increasingly different. The French political observer Alexis de Tocqueville believed he knew why. “I could easily prove,” he asserted in 1831, “that almost all the differences which may be noticed between the character of the Americans in the Southern and Northern states have originated in slavery.” And a quarter of a century later, neither Northerners nor Southerners liked developments on the other side of the Mason-Dixon line. “On the subject of slavery,” the Charleston Mercury declared, “the North and South . . . are not only two Peoples, but they are rival, hostile Peoples.” Even more than the cotton-based agriculture that dominated the region, slavery made the South different, and it was the differences between the North and South, not the similarities, that increasingly shaped antebellum American history.