The causes of the Civil War are a bit more complex than some people like to make it out as.
In the South, you had two main groups, the big plantation owners and the little farmers.
Initially, the little farmers were opposed to slavery, since only the big plantations could afford to buy a lot of slaves. That made it difficult for the little farmers to compete against the big plantations, and the little farmers would have gladly gotten rid of slavery to even out the playing field.
The big plantation owners based their entire way of life around slavery. Slaves provided cheap labor, and by keeping the lowest class enslaved, that also kept them from having any political power and any say in how the South was run.
In the North, the two biggest groups were the abolitionists and the industrialists. The abolitionists wanted to free the slaves for humanitarian reasons. Unlike how the Civil War is portrayed in a lot of history classes and textbooks, the abolitionists were not the majority and did not have the majority of political or financial power in the north. They were a constantly rising force though, and had been gaining in strength and numbers all through the 1800s. One thing to keep in mind though is that blacks were still considered to be inferior beings, even by the abolitionists. They just felt that even though blacks were inferior, that was no reason to keep them as slaves and to treat them poorly.
The northern industrialists wanted the country to focus on industry and abandon its agricultural roots. They felt that the world was moving to an industrial economy overall. In their eyes, the southern agriculturalists (which included both the big plantation owners and the small farmers) were holding back the entire U.S. economically. In general, the industrialists didn’t give two hoots about slavery one way or the other. Their focus was more on the economy.
These four distinct groups started fighting against each other politically in the early 1800s.
Back then, as now, instead of trying to come together and reach any kind of compromise that would satisfy everyone, whatever group ended up with the most votes in Washington basically forced their agenda down the other group’s throats. Sure, there were some compromises, just as there are today, but overall, these four groups kept fighting against each other.
As time went on, the small southern farmers realized that the northern industrialists were basically trying to ruin their entire way of doing things economically. So the southern farmers began to ally themselves with the big plantation owners, since they both wanted to keep an agricultural focus on the economy.
In the North, the industrialists and the abolitionists started teaming together, so that they could have more political strength.
Now you’ve got basically a north-south split.
As time went on, slavery began to become more and more the focus of the arguments, but there were other arguments too. When the industrialists and abolitionists managed to get enough votes in Washington to enact trade tariffs that benefited industry, South Carolina said that Federal trade tariffs didn’t apply to them, and this brought forth the issue of state rights and who had ultimate control of what.
Throughout the 1840s and 1850s, the two sides were roughly balanced, with the votes in Washington sometimes swaying one way and sometimes swaying the other, depending on which side happened to control more seats in Congress at the time. As time went on, more and more folks in the South started talking about secession. A lot of folks in the North, whether they were fine with slavery or not, did not want to see the country split in two.
Even though a lot of the causes of the Civil War were all in place by 1840 or so, folks back then weren’t all pissed off at each other enough to actually go to war. By the end of the 1850s though, that was no longer true. There had been so much political fighting for so long that everyone was pissed off and ready to fight.
What set everything in motion was the issue of the western territories. These territories were about to become states, and that meant that they would have votes and political power in Washington. Most people in the South really didn’t care whether or not people in the western territories had slaves or not, but they did care how these people would vote. If the western territories became slave states, then they would be allied with the other slave states in the South, and the balance in Washington would tip towards the South’s favor. If the territories became free states, then the balance would shift towards the North.
Lincoln did not start the war. He also did not tell the South that they couldn’t keep their slaves. While Lincoln was opposed to slavery, he told the South that he was willing to let them keep their slaves if it kept them in the Union. What Lincoln wouldn’t compromise on was the issue of the western states. As soon as Lincoln was elected, the South could see the writing on the wall. The western territories would become free states, and the balance of power would shift to the North. Once the North had control of Congress, they would enact laws, tariffs, etc. that would all benefit northern industrialists and abolitionists, which meant an eventual end to slavery and the entire southern way of life. At that point, the South felt that they had no choice, and seceded before Lincoln even took office.
And with that, the war was on.