The southern states almost seceded in the late 1820s and early 1830s.. and slavery didn't have anything to do with it.
Read some history boy!
Slavery had everything to do with it.
Missouri Compromise (Compromise of 1820) Missouri Compromise, legislative measures enacted by the United States Congress in 1820 that regulated the extension of slavery in the United States for three decades. When slaveholding Missourians applied for statehood in 1818, the long-standing balance of free and slave states (11 each) was jeopardized. A northern-sponsored amendment was then attached to the bill (1819) authorizing statehood; it prohibited the entry of slaves into Missouri and provided for the gradual emancipation of those already there. The proslavery faction was unable to prevent the bill's passage by the House of Representatives, where free states held a majority, but southern strength in the Senate defeated the bill.Maine, then a part of Massachusetts, also applied for statehood in 1819. Speaker of the House Henry Clay of Kentucky warned northern congressmen that unless they changed their position on Missouri the southerners would reject Maine's petition. To please the South the slavery restrictions for Missouri were then removed, and to satisfy the North, Senator Jesse B. Thomas (1777-1853) of Illinois introduced (February 1820) a proviso by which slavery would be prohibited forever from Louisiana Purchase territories north of 36° 30'. Southern extremists opposed any limit on the extension of slavery, but Clay maneuvered the measure through the House by a three-vote majority. Missouri and Maine were to enter statehood simultaneously to preserve sectional equality in the Senate. In 1821, when northern congressmen balked over antiblack clauses in Missouri's constitution, Clay again adjusted differences, and Missouri's admission was ensured.
The compromise became precedent for settling subsequent North-South disagreements over slavery and tariff issues, and it remained in effect until repealed by the Kansas-Nebraska Act of 1854.
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It was always about slavery and the expansion of slavery to the West. There was big money in slaves.
Learn some economics boy.
But why would the South want to secede? If the original American ideal of federalism and constitutionalism had survived to 1860, the South would not have needed to. But one issue loomed larger than any other in that year as in the previous three decades: the Northern tariff. It was imposed to benefit Northern industrial interests by subsidizing their production through public works. But it had the effect of forcing the South to pay more for manufactured goods and disproportionately taxing it to support the central government. It also injured the South?s trading relations with other parts of the world.
In effect, the South was being looted to pay for the North?s early version of industrial policy. The battle over the tariff began in 1828, with the "tariff of abomination." Thirty year later, with the South paying 87 percent of federal tariff revenue while having their livelihoods threatened by protectionist legislation, it became impossible for the two regions to be governed under the same regime. The South as a region was being reduced to a slave status, with the federal government as its master.
But why 1860? Lincoln promised not to interfere with slavery, but he did pledge to "collect the duties and imposts": he was the leading advocate of the tariff and public works policy, which is why his election prompted the South to secede. In pro-Lincoln newspapers, the phrase "free trade" was invoked as the equivalent of industrial suicide. Why fire on Ft. Sumter? It was a customs house, and when the North attempted to strengthen it, the South knew that its purpose was to collect taxes, as newspapers and politicians said at the time.
To gain an understanding of the Southern mission, look no further than the Confederate Constitution. It is a duplicate of the original Constitution, with several improvements. It guarantees free trade, restricts legislative power in crucial ways, abolishes public works, and attempts to rein in the executive. No, it didn?t abolish slavery but neither did the original Constitution (in fact, the original protected property rights in slaves).
Before the war, Lincoln himself had pledged to leave slavery intact, to enforce the fugitive slaves laws, and to support an amendment that would forever guarantee slavery where it then existed. Neither did he lift a finger to repeal the anti-Negro laws that besotted all Northern states, Illinois in particular. Recall that the underground railroad ended, not in New York or Boston-since dropping off blacks in those states would have been restricted-but in Canada! The Confederate Constitution did, however, make possible the gradual elimination of slavery, a process that would have been made easier had the North not so severely restricted the movements of former slaves.