From Letters of Note (http://www.lettersofnote.com):
In 1926, on discovering that his novel, “Arrowsmith,” had been awarded what was then called the Pulitzer Prize for the Novel, author Sinclair Lewis wrote the following letter to the Pulitzer Prize Committee and declined the honour. He remains the only person to have done so.
For Release Thursday, May 26th, 1926
To the Pulitzer Prize Committee,
Courtesy of Mr. Frank D. Fackenthal, Secretary,
New York City
I wish to acknowledge your choice of my novel “Arrowsmith” for the Pulitzer Prize. That prize I must refuse, and my refusal would be meaningless unless I explained the reasons.
All prizes, like all titles, are dangerous. The seekers for prizes tend to labor not for inherent excellence but for alien rewards: they tend to write this, or timorously to avoid writing that, in order to tickle the prejudices of a haphazard committee. And the Pulitzer Prize for novels is peculiarly objectionable because the terms of it have been constantly and grievously misrepresented….