Slaves, the south needed the slaves as a way of life because they had fields than they needed a lot of people working on and the north tried to free the slaves that the south depended on.
The major issue between the north and south in 1850s were segregation and the human riot between "blacks and whites".Racial injustice created disagreements between them .The blacks and whites soon had a war but separation didn't end there.Hope this helped !!!!!!