The american anti-slavery society increased membership because

Before the Civil War, the South relied heavily on salves because their labor was needed on the plantations. The South's wealth relied on the agriculture industry. In the North, inventions had made business easier to excel. Business was different in the North, and cities were urban rather than country like. You can see that slaves were not very important in the North. But, most in the North became abolitionists because they realized slavery would destroy the country. The Civil War happened not only to abolish slavery, but also to preserve the Union.