NEW YORK (AP).- A copy of the Emancipation Proclamation signed by President Abraham Lincoln that was purchased by Robert F. Kennedy sold Friday for more than $3.7 million, an auction record for a U.S. presidential document.

Kennedy bought the printed copy of the 1863 document declaring all slaves "forever free" shortly after its centennial celebration at the White House. It was sold for $3,778,500 to an anonymous bidder at Sotheby's by Kennedy's widow, Ethel. The price included a buyer's premium.

The maximum presale estimate was $1.5 million.

It's one of 48 printed copies signed by Lincoln. About half are known to survive; 14 are in public institutions, and eight to 10 are privately owned, Sotheby's said.

The original handwritten Emancipation Proclamation is in the National Archives.

The previous record was achieved at Christie's New York in February 2009 for Lincoln's 1864 victory speech after he was re-elected as president. It sold for $3,442,500, Sotheby's said.

Kennedy was attorney general to President John F. Kennedy and served as his brother's closest adviser. He was elected in 1964 to represent New York in the Senate and was assassinated in California on June 6, 1968, while campaigning for president.

Kennedy bought the copy, printed in black ink on acid-free paper, at a Sotheby's auction in early 1964 for $9,500.

The document marked a pivotal moment in Lincoln's presidency, and the country's, because it acknowledged that the Civil War was being fought to free the slaves.

A hundred years later, the United States found itself similarly torn over new laws enforcing black civil rights, and it was Robert Kennedy's job to carry them out.

Kennedy's copy was framed and hung in a main hallway of Hickory Hill, his 1840s home in McLean, Va.

The copy was one of 48 signed by Lincoln and printed to raise money for medical care for union soldiers. The RFK copy was first sold in the summer of 1864 at a Philadelphia fair held by the Sanitary Commission, a forerunner of the Red Cross.