Answer:
1) Slaves would have to be returned to their rightful owners, even if found in a free state. It truly enraged abolitionists, and Northern African Americans fled to Canada out of fear.
2) The work of the Underground Railroad resulted in freedom for many men, women, and children. It also helped undermine the institution of slavery, which was finally ended in the United States during the Civil War.
3) The abolitionist movement caused increasing friction between states in the North and the slave-owning South.