The American Civil War (1861-1865) officially began with the battle of Fort Sumter on April 12th-13th, 1861 and fundamentally shifted the trajectory of American history. Arguably the first instance of modern total war for the United States, the war impacted virtually every facet of American society. However, different perceptions of its origins and legacy persist across regions and demographics in the United States. One of the most contentious differences in opinion is around what the primary cause of the Civil War is.
Slavery
Slavery was prevalent throughout the South due to its primarily agrarian economy. While the majority of the Southern population did not own slaves themselves, slavery still held great social and political influence across the region.
Prevalence of white supremacy
White supremacy was prevalent across all levels of Southern society due to the historical presence of slavery in its agrarian economy.
The election of Abraham Lincoln, representing the young abolitionist Republican Party, in the 1860 Election was the tipping point for many Southerns to actually secede.
Northern abolitionist John Brown failed to launch an armed slavery insurrection at Harper's Ferry, Virginia on October 16-18, 1859. The failed insurrection gave rise of suspicion among Southerners of a Northern conspiracy to launch slave revolts across the South.
Under a specific interpretation of the American, it was outside of the Federal Government's jurisdiction to outright restrict a state institution - including slavery.
Limited Federal government power
Under the American Constitution, the Federal government could not impose the removal of institutions installed by State governments.
By the 19th century the United States was rapidly expanding westward with new states being formed and admitted into the Union. The two coalitions of Free and Slave states jockeyed to maintain power in the Senate with newly formed states joining either coalition. This balance of power was broken by 1958, favoring the Free State Coalition.