How did the abolition of slavery unfold around the world?

The answer

The abolition of slavery was a gradual, uneven process spanning centuries. Haiti became the first nation to abolish slavery through revolution in 1804. Britain's Slavery Abolition Act of 1833 freed 800,000 enslaved people across the empire but paid £20 million (equivalent to £17 billion today) to the slave owners as 'compensation' - a debt British taxpayers were still paying off until 2015. The United States abolished slavery via the 13th Amendment in 1865 after a civil war that killed 620,000 people. Brazil was the last Western Hemisphere nation to abolish it in 1888.