That's what the victors wrote in the history books. It is largely a lie. Slavery was already dying out. The South was industrializing, and doing it better and cheaper than the North. That frightened the entrenched elite in the northeast manufacturing enclaves. The recasting of Southerners as barbaric inhumane slave-holders was necessary not just to make war more palatable, but to stir up the average Northern to support an effort he would not support if the facts were known. The propaganda worked.
As I stated earlier, there were more abolitionist organizations in the South than there ever were in the North. The North was treating the South as an agricultural colony, and like England did to its American colonies, taxed them almost into bankruptcy for shipping goods that didn't ever leave the country, but simply went north.
Another thing I've learned recently is that the Northeast, where the industrialists that wanted to destroy the South had their factories and families, was largely against the original Revolution, being a hotbed of Tories and spies. Two generations later, the children of those traitors were plotting to undermine the limited-government constitutional guidelines and establish a more centralized, authoritarian government.
Their first real victory in that area was getting James Buchanan elected president after Millard Fillmore and Franklin Pierce managed to steer the country to at least a stalemate over Southern industrialization and westward expansion -- issues the North vehemently opposed.
The irony is that history will tell you that Fillmore was a "do-nothing" and Pierce a divider. The reality is that both saw the benefits of letting the South alone to modernize and expand economically to whatever extent businessmen and bankers wanted to invest in the efforts, benefits that would eventually make the whole country better, more prosperous, and put a natural, peaceful end to slavery.
The Northern industrialists hidden agendas of centralized authoritarian government and concentration of wealth in the pockets of those few individuals demanded they undermine those efforts and destroy the South. With Buchanan and Lincoln, they achieved their goals. Today's liberals are the direct descendants of those anti-American activists, having traded economics for politics as their chief tool to achieve their ends.
The U.S. would not be the U.S. today if the South had won, but the CSA would be the stronger, freer nation in which to live. I believe the two nations would have been at each others' throats all this time, and whatever the North became would be Marxist in socioeconomic philosophy.