Respuesta :
Men were needed to work in war-related industries in the North. Most white men were being drafted, while draft boards were so racist that blacks tended to be excluded, and available to fill the industrial jobs.
While the army was at war, many jobs opened up that otherwise would not have. The Army took up many workers, and the arms industry expanded.
The south, in the meantime, was stagnating. Traditional employment in the south was working to capacity and the north looked like worthwhile greener pastures.