I apologise if this topic is covered but I couldn't find anything specifically to this.
Historians of Reddit more versed in this area than me - would you say that the American civil war was primarily about the moral and societal aspects of slavery or the financial aspects?
(Basically was it actually about slavery primarily or was it primarily about money with slavery as the economic issue.)
Edit: spelling mistake.
The southern states seceded first and foremost in order to preserve the institution of slavery. Not only is that my opinion, and the opinion of any historian worth his salt, but they flat out say it several times.
The Confederate Constitution states in Article 1, Section 9 (Limits on Congress, Bill of Rights):
No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed.
Right there they say that no matter what you are allowed to own slaves.
Or Article 4, Section 3 (New States):
...States to be admitted into the Confederacy. In all such territory the institution of negro slavery, as it now exists in the Confederate States, shall be recognized and protected...
Any territory that may have been acquired had the rebellion seceded would have also been slave territory.
The Vice President of the Confederacy, Alexander Stephens, stated in his inaugural address:
Our new government... its corner- stone rests, upon the great truth that the negro is not equal to the white man; that slavery subordination to the superior race is his natural and normal condition
Now let's see what the individual states had to say about it. Mississippi outright declares that
Our position is thoroughly identified with the institution of slavery--
The Georgia declaration of secession answers the question of why they were seceding very succinctly:
Why? Because by their declared principles and policy they have outlawed $3,000,000,000 of our property
They being the Republican party and what do you think that property is?
South Carolina says they are seceding because:
...of President of the United States, whose opinions and purposes are hostile to slavery.
If that isn't enough for you not only did the southern states declare that they were seceding in order to not lose their slaves but northern soldiers believed they were fighting to end slavery. The Battle Hymn of the Republic was a common patriot song sung by soldiers and civilians alike and within its lyrics it says that fighting to end slavery is enacting God's will.
In the beauty of the lilies Christ was born across the sea, With a glory in His bosom that transfigures you and me. As He died to make men holy, let us die to make men free, While God is marching on.
Some people also make the claim that Lincoln fought the war not to end slavery but to keep the union together but this means you have to explain why Lincoln expressed his grievances against slavery on the basis of morality long before he became president.
In an 1854 speech in Peoria he said:
I can not but hate [the declared indifference for slavery's spread]. I hate it because of the monstrous injustice of slavery itself. I hate it because it deprives our republican example of its just influence in the world -- enables the enemies of free institutions, with plausibility, to taunt us as hypocrites -- causes the real friends of freedom to doubt our sincerity, and especially because it forces so many really good men amongst ourselves into an open war with the very fundamental principles of civil liberty -- criticising [sic] the Declaration of Independence, and insisting that there is no right principle of action but self-interest.
In Chicago in 1858 he said:
I have always hated slavery, I think as much as any Abolitionist. I have been an Old Line Whig. I have always hated it, but I have always been quiet about it until this new era of the introduction of the Nebraska Bill began. I always believed that everybody was against it, and that it was in course of ultimate extinction.
17 Sept. 1859 in Cincinnati:
I think Slavery is wrong, morally, and politically. I desire that it should be no further spread in these United States, and I should not object if it should gradually terminate in the whole Union.
I hope I have demonstrated with sufficient primary documents and quotes that the southern states did indeed secede first and foremost because of slavery and that both Lincoln and the north were actually fighting to end that "curious institution".