What historical reasons did the northerners abolish slavery?

The northerners didn't need slavery because their main economy is manufacturing at factories.
Because they didn't have anything to do with slavery, they viewed it with a critical eye.

The southerners had slavery because they had giant plantations to farm cash crops. The soil was futile and had a suitable climate.

Contributing factors  leading  to the harlem renaissance were the great migration of african americans to northern cities, which concentratedambitious  people in places where they could encourage each  other, and the first world war, which had created new industrial work opportunities for tens of thousands of people.