Explanation: The north was always populated to begin with since the living standards were a lot higher than in the south. And when the northern states "forbided" slavery a mass migration of African Americans from southern states moved to the northern states. They migrated to find a better life up in the north(before the civil war). When president lincoln gave the to go sign that African Americans were able to enlist in the army during the American civil war it gave the North a manpower increase, one that the south didn't have since the south did not allow African Americans to be enlisted in thir arms.
