Abraham Lincoln signed it. A lot of scholars say he didn’t write it. Now, newly discovered evidence helps solve an enduring mystery.

In a records box in a back office in a house in the hills of Vermont, six letters about Abraham Lincoln’s famous “letter to the Widow Bixby” lay unknown and undisturbed. For how long is uncertain, although this author’s fingerprints made last March were the only ones visible in the thick chalky dust of years. The letters, received and written by Robert Todd Lincoln within a span of eight weeks in late 1925, point to a son’s knowledge—and a friend’s knowledge—about who really wrote the Bixby letter.

Considering that this is one of the most enduring and indefatigable mysteries in all Lincoln lore, how is this new discovery possible? The answer lies in the simple truth that scholars have long overlooked Robert Todd Lincoln, believing him a minor character in the Lincoln legend. He is perceived as cold and aloof, a Todd more than a Lincoln, and a son dissociated from his famous father. Many think that the naturally reticent Robert said little of consequence about his father and that everything of value he owned concerning him was given to the Library of Congress in 1919 or resides in Springfield, Illinois, at the new Abraham Lincoln Presidential Library and Museum. None of this is true.

The Bixby letter is famous for its perfect use of the English language. Along with the Gettysburg Address and Second Inaugural, it is one of Lincoln’s most revered literary legacies. The letter was published in the Boston Transcript on November 25, 1864, the same day Mrs. Bixby received it:

“Dear Madam,—I have been shown in the files of the War Department a statement of the Adjutant General of Massachusetts, that you are the mother of five sons who have died gloriously on the field of battle.

“I feel how weak and fruitless must be any words of mine which should attempt to beguile you from the grief of a loss so overwhelming. But I cannot refrain from tendering to you the consolation that may be found in the thanks of the Republic they died to save.

“I pray that our Heavenly Father may assuage the anguish of your bereavement, and leave you only the cherished memory of the loved and lost, and the solemn pride that must be yours, to have laid so costly a sacrifice upon the altar of Freedom.

“Yours, very sincerely and respectfully,

“A. Lincoln”

Controversy has raged for 80 years about whether the President actually wrote these words.

The letters quoted [in the article] prove not only that Robert Lincoln believed his father had written the Bixby letter but also that John Hay himself told Robert he’d had nothing to do with it.

So we come to a satisfying conclusion: America’s greatest President wrote America’s greatest letter.