From the Lawrence Daily Journal-World for Mar. 6, 1971:

For some time, the Journal-World’s editorial page had included a large quotation at the top, “I do not agree with a word that you say, but I will defend to the death your right to say it,” attributed to Voltaire. However, the newspaper had recently received an anonymous letter denying the source of the quotation, saying, “You would be safe in offering a $100 reward to anybody finding the statement in Voltaire.” Editors questioned James Seaver, director of the Western Civilization program at Kansas University, and he responded that the quotation was believed to be apocryphal. Seaver referred the editor to Charles Warner, KU professor of history specializing in 18th century France, who said that if the quotation were in fact not authentic, the Journal-World was not the first to use it as a heading for an editorial page. “Mail on the subject swelled to a trickle today,” the article concludes, “as the postman brought still another missive questioning the quote.”