The Tariff of 1828 was a very high protective tariff that became law in the United States in May 1828. It was a bill designed to fail in Congress because it was seen by free trade supporters as hurting both industry and farming, but it passed anyway. The bill was vehemently denounced in the South and escalated to a threat of civil war in the Nullification Crisis of 1832–33. The tariff was replaced in 1833, and the crisis ended. It was called the "Tariff of Abominations" by its Southern detractors because of the effects it had on the Southern economy. It set a 38% tax on some imported goods and a 45% tax on certain imported raw materials.

A consensus of historians who address the origins of the American Civil War agree that the preservation of the institution of slavery was the principal aim of the eleven Southern states that declared their secession from the United States and united to form the Confederate States of America. However, while historians in the 21st century agree on the centrality of slavery in the conflict, they disagree sharply on which aspects of this conflict were most important, and on the North's reasons for refusing to allow the Southern states to secede. Proponents of the pseudo-historical Lost Cause ideology have denied that slavery was the principal cause of the secession, a view that has been disproven by the overwhelming historical evidence against it, notably the seceding states' own secession documents.