His most famous words - "I have a dream" - were extemporized.
And he routinely delivered whole sermons from memory.
But as an extraordinary exhibition of his papers, books and other documents at Sotheby's auction house in New York makes clear, the Rev. Dr. Martin Luther King Jr. was an inveterate scribbler who jotted down thoughts and outlined speeches on the backs of envelopes and church programs. He also scrawled entire essays in the flyleaves of paperbacks.
Occupying 20,000 square feet - nearly one floor - of the auction house, the sprawling exhibition opened to the public yesterday and runs through Sept. 8. Sotheby's is offering the collection for private sale - not at auction - on behalf of the King estate.
Among the vast array of items on display are more than 7,000 documents in King's handwritng, from the blue book in which he wrote a Bible class examination while a student at Morehouse College.
A diary that he kept while jailed for civil disobedience in 1962 and the notepaper on which he drafted his Nobel Peace Prize acceptance speech in 1964, four years before his assassination, are also on display.
There is also a rare typewritten early draft of the "I Have a Dream" speech, of which only one paragraph made it into the final version.
David N. Redden, a vice chairman of Sotheby's, called the collection "the most important non-presidential archive of the 20th century in this country."
Though never exhibited to the public, the collection made headlines in 1999 when the Library of Congress tried to buy it. Sotheby's had appraised it at $30 million, and the King estate agreed to sell it to the library for $20 million - a record amount for the institution.
Congress voted to authorize the money, but the deal collapsed in committee hearings when House members questioned the expense. Some argued that the purchase would be a bad precedent, discouraging donations - the traditional practice and the way the library has acquired the papers of civil-rights-era figures like Bayard Rustin and A. Philip Randolph.
While some of the material at Sotheby's was previously housed at The King Center in Atlanta and is familiar to scholars, much of it has been in storage at the Atlanta home of King's widow, Coretta Scott King.
Dozens of handwritten sermons, sermon outlines and other religious writings from the 1950s and early '60s, as well as King's personal library are included in the collection.
Among its 1,000 volumes are annotations in books that offer tantalizing hints of how he developed signature themes and verbal motifs.
In a 1954 book of sermons by J. Wallace Hamilton, on the first page of a chapter titled "Shattered Dreams," King penciled an outline for a sermon emphasizing dreams, with sections headed "When a dream becomes an illusion" and "Why this dream can never come true."
"I had forgotten, until I saw it all laid out, how prolific he was and how much there is in his own handwriting," Coretta Scott King said.
"For someone who was as busy as he was and yet took the time while those campaigns were going on to produce so much material, it's truly amazing."
Redden said that Sotheby's was shopping the collection to a select group of universities, libraries and government agencies, though he declined to identify them.
There is no fixed asking price, he said, though he added "certainly, $20 million would not be an unreasonable sum at all."
Coretta Scott King said that the family's goal was to see the collection placed in a single institution that could guarantee public access to the materials and their long-term preservation. The King estate will retain control over copyrights, she said.