You are looking at the malignancy of the Democratic Party, which was stripped of its slave plantations of the south and moved into the urban areas of the north, to insinuate themselves into unions and the "working class" by way of Karl Marx.

Blacks were refugees from the postbellum south because the Democrat Party was still in control with lynchings and ballot suppression, and the northern cities offered the prospect of wage labor. This went on for a while, with the blacks rising in standing, until the Democrats conceived a way to cripple them by an old enslavement tactic: break up the family and destroy the male lineage through fatherhood. It was called welfare, and paid poor mothers if they had no husband. The resulting large clutch of children had no father to learn from, and they joined gangs to attain their adulthood. The result of this travesty shows up in bullets on Chicago weekends.

The south was a rising slave power, ruled by Democrats. The Republicans were formed as an abolitionist party and won their first election with Lincoln. Due to the limitations on slavery in new states admitted to the Union, the south correctly saw that slavery was doomed---as the future Union would have a majority of abolitionist states---so it decided to confederate and secede while the getting was good. Any other motive was window-dressing. This was well understood at the time. My great-great-grandfather was in the Army of Illinois and his words to my great-grandfather were that the War was always about slavery.

Apologists for the south like to appeal to notions of chivalry and family. But the north were all families descended from pioneers and those who settled the midwest---and the practice of slavery was the antithesis of chivalry. It was the triumph of evil.