Final answer:
The abolitionist movement began in the United States in the 19th century, with enslaved Africans running away or rebelling against their masters. It gained momentum in the 1830s, led by prominent figures like William Lloyd Garrison and Frederick Douglass who called for immediate emancipation and the end of slavery.
Step-by-step explanation:
The abolitionist movement began in the United States during the first half of the nineteenth century. Enslaved Africans started running away from their masters or organizing rebellions to fight for freedom. Numerous slave rebellions and uprisings took place from the seventeenth century up to the Civil War, with over 250 instances documented. The movement gained momentum in the 1830s, led by figures like William Lloyd Garrison and Frederick Douglass, who advocated for immediate emancipation and the end of slavery.