More than 10,000 books and manuscripts from the private collection of Martin Luther King Jr are to be put under the hammer later this month.
Mr King's campaigning transformed the lives of black Americans
Among the items are more than 7,000 handwritten papers, as well as an early draft of his "I have a dream" speech.
The auction, which comes 38 years after the US civil rights was leader shot dead, will take place on June 30.
The collection will be sold as a single lot and is expected to raise up to $30m (£16.3m) for the King estate.
Ahead of the sale, the entire collection, which spans the period between 1946 and 1968, will be put on display for the public to view.
Among the documents up for sale at the Sotheby's auction is a telegram inviting Mr King to President Lyndon Johnson's signing of the 1965 Voting Rights Act, which granted political power to southern black people.
It also includes a draft of his speech on accepting the Nobel Peace prize in 1964, as well as manuscripts he was working on when he was shot dead in April 1968.
The collection also contains more than 1,000 volumes, including more than 50 books and pamphlets about Mahatma Gandhi, the peaceful leader of Indian independence.
Announcing the auction, Sotheby's described the collection as "the most important American archive of the 20th century in private hands".
The auction was sanctioned just four months after the death of Mr King's widow, Coretta Scott King.