The southern states were allowed to secede from the United States in 1861 without causing a Civil War with its immense loss of life. The Union tried to bribe the border states who had slaves not to join the southern Confederacy but failed. Most of the Western states and territories who had slaves also seceded and joined the Confederacy, though the northern states still had twice the population of the Confederacy and almost all of the heavy industry in America. The Confederate States of America still had cotton and tobacco, and traded primarily with Britain who profited from its own cotton-weaving mills throughout England.
The North had its heavy industry and its population largely of European immigrants. Some Western states, such as California and Oregon, with few slaves, sided with the North, whereas the mid-western and southern states with slaves sided with the South. The Confederacy planned on invading and occupying its southern neighbors, such as Mexico and the Caribbean, though there were few resources in those areas, and the Confederacy would have to purchase all its machinery and weapons from England or from the North, though the North would sell them no armaments. However, the South did have some shipyards to construct a navy and merchant vessels. The South held its millions of slaves for the production primarily of cotton. The South did not thrive; they had to support their slaves and they possessed a large population of poor, uneducated, unemployed and often unemployable whites numbering up to five million. These whites were not allowed to migrate across the borders to the North, so many of them began to move to the mid-west and western areas, putting great stress on those economies in addition to the stress they created in the South. The North continued to thrive with its well-established industries, which included cloth mills which were sold much of the cotton from the South. So the North as well as Britain were profiting from slavery which lowered the cost of cotton to them.
The North didn't want the slaves to come North; they didn't want to support them and were themselves racist. Lincoln had proposed to the Blacks in the North that they have their own country to be purchased by the United States somewhere in South America to which all the free Blacks would be sent, but the Blacks had balked at this, stating that they were more American than the white Americans, for their families had been in America for three hundred years. Lincoln knew that the slaves of the South were its primary resource and that cotton would die without their labor. The North sent Blacks into the South to preach rebellion among the slaves and also secreted arms to be used in such a rebellion.
But very soon, within five years, the Southern production of cotton began to fall drastically due to overused land that was no longer productive and also to drought, as well as a restive slave population that had on occasion turned on its masters and burned plantations. The Confederacy was imploding. And then the border states of the Confederacy petitioned for reentry into the Union. And states in the Confederacy began to rebel against their government led by Jefferson Davis and the plantation owners. The plantation owners began fighting among themselves. As their need for slaves diminished as their cotton diminished, they tried selling their slaves, whose value became nil. But they were afraid to send their slaves to the North, rightfully fearing the vengeance and violence of hundreds of thousands of slaves freed from their plantations. Within five years the Confederacy folded. Britain, with no reason to support them without cotton, rekindled friendships with the North. The South became worse than a third-world nation: deadly family feuds, religious wars, culture wars erupted everywhere; people starved. The mid-western states became battlegrounds for these same warring groups. Every southern state now turned to the North for help, for food.
The North eventually allowed all the Confederate States back in the Union. The slaves had all found their own freedom when the plantations failed and they became obsolete as human property. The North broke up the plantations and gave land to the Blacks, which was greatly resented by the large population of poor southern whites, who were eventually coopted by the old powerful families of the South, and were willingly used to "put the Blacks in their place" via the Jim Crow laws. This became much easier as the southerners again took control of the American Congress and Senate and pushed their racist policies. And so it remains to this day as is evident in the Republican Party.