The estate of the Reverend Martin Luther King, Jr will auction the civil rights leader’s entire collection of more than 10,000 documents, including the text of his famous 1963 “I have a dream” speech, as a single lot this month.

“This collection is without question the most important American archive of the 20th century in private hands,” said David Redden, the vice-chairman of Sotheby’s, the auctioneer that will conduct the sale on June 30.