Historiography examines how the past has been viewed or interpreted. Historiographic issues about the American Civil War include the name of the war, the origins or causes of the war (slavery or states' rights), and President Abraham Lincoln's views and goals regarding slavery.
The question of how important the tariff was in causing the war stems from the Nullification Crisis, which was South Carolina's attempt to nullify a tariff and lasted from 1828 to 1832. The tariff was low after 1846, and the tariff issue faded into the background by 1860 when secession began. States' rights was the justification for nullification and later secession. The most controversial right claimed by Southern states was the alleged right of Southerners to extend slavery into territories acquired by the United States.
Under Lincoln's leadership, the war was fought to preserve the Union. However, as the war evolved in response to political and military issues, Lincoln decided in 1862 that slavery had to end in order for the Union to be restored. He was faced with the questions of how to free the slaves and, once they were free, what their legal and economic status would be.