Short answers, pulled from the story.
Louis X, king of France, published a decree in 1315 proclaiming that any slave setting foot on French soil should be freed. This legal declaration prompted subsequent governments to circumscribe slavery in the overseas colonies.
France was the first country to fully outlaw slavery in 1315 through a royal decree issued by King Louis X. Although later used in its colonies, this initial act established the legal principle that France signifies freedom for those who set foot on its soil.
Abraham Lincoln issued the Emancipation Proclamation on the 1st of January 1863 which changed the legal status of 3 million slaves in the Confederacy from slave to free. The Union Army liberated all slaves in the Confederacy by Juneteenth on the 19th of June 1865.
William Wilberforce led the parliamentary campaign while Thomas Clarkson gathered vast amounts of data as the group's most prominent researcher. They formed the Society for Effecting the Abolition of the Slave Trade in London in 1787 to push for legislative change.
Mauritania is the latest country to officially abolish slavery with a presidential decree in 1981. This action followed earlier abolition dates in Saudi Arabia, Yemen, Dubai, and Oman during the mid-20th century.