Abolitionists were groups of people - for example, the American Anti-Slavery Society - who campaigned for the abolition of slavery in the USA. They were more active in the northern states than in the southern ones.
When were the abolitionists active in the USA?
The abolition movement started in the eighteenth century. However, it gained traction from 1833, after the abolition of slavery in the British Empire. It ended after the emancipation of slaves in 1865.
What did abolitionists campaign for in the USA?
The Anti-Slavery Society campaigned for abolition, and civil rights for ex-slaves. The society, and other organisations, helped the abolition debate enter American politics, and increased friction between northern and southern states.