I think the answer is that The 1850s was a pivotal decade in the 19th century. In the United States, tensions over slavery became prominent and events began to put the nation on the road to civil war. In Europe, new technology was celebrated and the great powers fought the Crimean War.
Answer: To abolish slavery.
Explanation: The 13th amendment to the United States Constitution provides that "Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction."
Decolonization allowed a nation to establish and maintain independent territories.
