Many southerners defended slavery as a "great moral, social, and political blessing"—far superior to the wage "slavery" of the North. Yet there was increasing opposition. Some decried its economic inefficiency. Others saw it an impediment to the growing republic. Slaves could go back to Africa but not into the new territories of the United States.
At the core of the opposition were those who objected to slavery on moral and humanitarian grounds. This group was an extension of other social movements of the time and an intellectual heir of the Transcendentalists. Located throughout the Northeast with a strong New England presence, proponents called for the complete abolition of slavery throughout the Union and its territories. They provided aid for those who bravely ran away, supplying guidance, resources, and safe harbor along the Underground Railroad.