A manuscript copy of the 13th amendment signed by Abraham Lincoln has sold for $2.4m at Sotheby's in New York.
The document, which abolished slavery, dates to February 1, 1865 and is signed by 36 senators.
It's one of very few surviving copies of this foundational piece of US history.
Lincoln was morally opposed to slavery and saw its eradication as crucial to the development of the United States.
He wrote in 1855: "Our progress in degeneracy appears to me to be pretty rapid.
"As a nation, we began by declaring 'all men are created equal.' We now practically read it 'all men are created equal except negroes.'
"When the Know-Nothings get control, it will read 'all men are created equal, except negroes, and foreigners, and catholics [sic].'"
It was not technically necessary for Lincoln to sign the document, but his conviction was such that he wanted to be seen to put his name to it.
While the amendment abolished slavery, racism remained endemic. In the south, black people continued to toil in slavery, in all but name, for decades afterwards.
Lincoln's signature is not particularly rare, but demand is high - even among non-collectors.
Items associated with key moments in his presidency are particularly sought after, with a manuscript copy of his second inauguration speech selling for $3.4m in 2009.
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