Although there is little disagreement among historians on the details of the events that led to war, there is disagreement on exactly what caused what and the relative importance. There is no consensus on whether the war could have been avoided, or if it should have been avoided.
On the eve of the Civil War, the United States was a nation divided into three distinct regions: New England and the Northeast had a rapidly growing industrial and commercial economy and an increasing density of population, fed by large numbers of European immigrants, especially Irish, British and German. The Midwest ("Northwest") was a rapidly expanding region of free farmers tied to the East by railroads, and to the South by the Mississippi riverboats. South had a settled plantation system based on slavery, with rapid growth taking place in Texas. The economic systems were based on free labor in the North and on slave labor in the South (Beale 34-35).
More serious as a cause of the war were divergent moral value systems. Moral arguments against slavery had long existed, but, in the interest of maintaining unity, party loyalties had mostly moderated opposition to slavery, resulting in compromises, such as the Missouri Compromise of 1820 and the Compromise of 1850. Increasingly moralism meant that people would not compromise their principles. It was all or nothing. The "house divided cannot stand," said Lincoln.
In 1854 the old two-party system broke down after passage of the Kansas-Nebraska Act. The Whig Party disappeared, and the new Republican Party arose in its place. It was the nation's first major political party with only sectional appeal; though it had much of the old Whig economic platform, its popularity rested on its commitment to stop the expansion of slavery into new territories. Open warfare in the Kansas Territory, the panic of 1857, and John Brown's raid on Harper's Ferry further heightened sectional tensions and helped Republicans sweep elections in 1860. In 1860, the election of Abraham Lincoln, who met staunch opposition from Southern slave-owning interests, triggered Southern secession from the union.
During the secession crisis, many politicians argued for a new sectional accommodation to preserve the Union, focusing in particular on the proposed "Crittenden Compromise." But historians in the 1930s such as James G. Randall argued that the rise of mass democracy, the breakdown of the Second Party System, and increasingly virulent and hostile sectional rhetoric made it highly unlikely, if not impossible, to bring about the compromises of the past (such as the Missouri Compromise and the Compromise of 1850). Indeed, the Crittenden Compromise was rejected by Republicans. One possible "compromise" was peaceful secession agreed to by the United States, which was seriously discussed in late 1860-and supported by many abolitionists-but was rejected by Buchanan's conservative Democrats as well as the Republican leadership.
Most historians agree, following Ulrich B. Phillips, Avery Craven, and Eugene Genovese, that the South had grown apart from the North psychologically and in terms of its value systems. One by one the common elements that bound the nation together were broken. For example the major Protestant