Arguments that the Civil War was inevitable
* The issue of slavery was a major factor in the lead-up to the Civil War. The Southern states were heavily dependent on slavery, while the Northern states were increasingly opposed to it. This difference in opinion led to a number of conflicts, including the Kansas-Nebraska Act of 1854 and the Dred Scott decision of 1857.
* The sectional divide between the North and the South was also a major factor in the outbreak of the Civil War. The North was becoming increasingly industrialized, while the South was still largely agricultural. This difference in economies led to a number of conflicts, including the Tariff of 1832 and the Compromise of 1850.
* The election of Abraham Lincoln as president in 1860 was the final straw for many Southerners. Lincoln was a member of the Republican Party, which was opposed to slavery. This led many Southerners to believe that their way of life was under threat, and they began to secede from the Union.
Arguments that the Civil War could have been avoided
* Some historians argue that the Civil War could have been avoided if the Southern states had been willing to compromise. For example, the South could have agreed to gradual emancipation or to the admission of new free states into the Union.
* Other historians argue that the Civil War could have been avoided if the North had been more understanding of the South. For example, the North could have agreed to protect the institution of slavery in the Southern states.
Ultimately, the question of whether the US Civil War was necessary is a matter of perspective. There are valid arguments to be made on both sides of the issue.