( AP )- One of the most significant collections of Abraham Lincoln letters to be auctioned in decades includes his heartfelt reply to a group of youngsters who asked him to free America's "little slave children."
The 1864 letter is expected to fetch the highest price ever for a Lincoln manuscript.
"Please tell these little people I am very glad their young hearts are so full of just and generous sympathy," the president wrote in the letter to a woman who had mailed their petition from Concord, Mass.
Lincoln's hand-penned reply, estimated to be worth $3 million to $5 million before the April 3 auction at Sotheby's, could become the most expensive Lincoln letter ever sold.
Also on the block are more than 100 manuscripts written by other presidents and major American historical figures.
Thomas Jefferson reports on his debilitating monthlong migraine headache and George Washington's failing health. The ambidextrous Jefferson wrote most of the letter with his left hand and a postscript with his right.
Some of the writings touch on topics relevant even today, such as the acrimony among politicians.
An 1862 letter from former President Millard Fillmore excoriates Lincoln for expanding his war powers, calling him a "tyrant" who "makes my blood boil."
The president who guided the nation through the Civil War was inundated with mail from ordinary people but could only occasionally answer personally.
He was deeply moved by the simple request he received in April 1864 from the Massachusetts children, reading: "Children's Petition to the President asking him to free all the little slave children in this country."
It was signed by 195 boys and girls.
Lincoln answered with a passionate expression of his desire to end slavery, saying it was God's will to free slave children "and that, while I have not the power to grant all they ask, I trust they will remember that God has, and that, as it seems, He wills to do it."
By 1864, Lincoln had signed the Emancipation Proclamation, which declared millions of slaves free, but all of them were not freed until July 1865.
The highest price paid for a Lincoln manuscript until now is $3.1 million, for a speech outlining his strategy for postwar reconstruction sold at Christie's in New York in 2002.
The manuscript collection, worth as much as $12 million, is to go on public exhibition starting March 29.
The letters, collected by New York physician Robert Small, represent the greatest concentration of Lincoln letters on the block since the early 1980s, said Selby Kiffer, an American manuscript expert at Sotheby's.