<P> The causes of secession were complex and have been controversial since the war began, but most academic scholars identify slavery as a central cause of the war . James C. Bradford wrote that the issue has been further complicated by historical revisionists, who have tried to offer a variety of reasons for the war . Slavery was the central source of escalating political tension in the 1850s . The Republican Party was determined to prevent any spread of slavery, and many Southern leaders had threatened secession if the Republican candidate, Lincoln, won the 1860 election . After Lincoln won, many Southern leaders felt that disunion was their only option, fearing that the loss of representation would hamper their ability to promote pro-slavery acts and policies . </P> <P> Slavery was a major cause of disunion . Although there were opposing views even in the Union States, most northern soldiers were largely indifferent on the subject of slavery, while Confederates fought the war largely to protect a southern society of which slavery was an integral part . From the anti-slavery perspective, the issue was primarily about whether the system of slavery was an anachronistic evil that was incompatible with republicanism . The strategy of the anti-slavery forces was containment--to stop the expansion and thus put slavery on a path to gradual extinction . The slave - holding interests in the South denounced this strategy as infringing upon their Constitutional rights . Southern whites believed that the emancipation of slaves would destroy the South's economy, due to the large amount of capital invested in slaves and fears of integrating the ex-slave black population . In particular, southerners feared a repeat of "the horrors of Santo Domingo", in which nearly all white people--including men, women, children, and even many sympathetic to abolition--were killed after the successful slave revolt in Haiti . Historian Thomas Fleming points to the historical phrase "a disease in the public mind" used by critics of this idea, and proposes it contributed to the segregation in the Jim Crow era following emancipation . These fears were exacerbated by the recent attempts of John Brown to instigate an armed slave rebellion in the South . </P> <P> Slavery was illegal in much of the North, having been outlawed in the late 18th and early 19th centuries . It was also fading in the border states and in Southern cities, but it was expanding in the highly profitable cotton districts of the rural South and Southwest . Subsequent writers on the American Civil War looked to several factors explaining the geographic divide . </P> <P> Sectionalism refers to the different economies, social structure, customs and political values of the North and South . Regional tensions came to a head during the War of 1812, resulting in the Hartford Convention which manifested Northern dissastisfaction with a foreign trade embargo that affected the industrial North disproportionately, the Three - Fifths Compromise, dilution of Northern power by new states, and a succession of Southern Presidents . Sectionalism increased steadily between 1800 and 1860 as the North, which phased slavery out of existence, industrialized, urbanized, and built prosperous farms, while the deep South concentrated on plantation agriculture based on slave labor, together with subsistence farming for poor freedmen . In the 1840s and 50s, the issue of accepting slavery (in the guise of rejecting slave - owning bishops and missionaries) split the nation's largest religious denominations (the Methodist, Baptist and Presbyterian churches) into separate Northern and Southern denominations . </P>

States that took part in the civil war