Yet, even as the North did not want a mass migration of freed slaves, the North long had a substantial and prosperous population of free Blacks before the Civil War, sometimes with remarkable biographies impossible for free Blacks in the Old South.
There are, for example, Pierre Toussaint, a former Haitian slave. A hairdresser in New York, his talent and good spirit made him prosperous and his devout Catholic faith led him to a life of virtue and generosity. He is now honored as Venerable and on the path to full sainthood. Pierre Toussaint's remains lie in the crypt below the main altar of Saint Patricks, the first layman interred there.
Or consider Solomon Northup, a free black from Maryland who was kidnapped and sold into slavery in the South. Eventually, after twelve years, he was able to get a letter to his family. They mobilized Maryland's officials on his behalf, and Louisiana authorities helped by issuing writs and sending deputies to rescue Northup. He returned home and wrote a remarkable and lucid account of his experience.
Instead of secession and a civil war, the South ought to have remained in the Union and sought a national plan for gradual, compensated emancipation. Out of pride and arrogance though, the South rejected the Constitution because Lincoln was elected with a platform that would have mildly limited the expansion and enforcement of slavery.
In defeat, the South's partisans spun an elaborate false tale of the South as a victm of unconstitutional machinations. Go back and read the speeches and articles of secession by the Southern states. They make quite clear that secession and the civil war were about keeping slavery without compromise and little else.
The north voted for the original thirteenth amendment which would have enshrined slavery forever in an effort to keep the south from leaving the union. Slavery was NOT why the south left. They also knew that war with the north would be futile so they did not want war either. The north did not want to see it's cash cow leave the union and decided that forcing the issue into a war was the answer to it's problem. This is the truth of what happened no matter how you try to spin your account. The north won and EVERYBODY lost.