A portrait of George Washington by Gilbert Stuart sold for $8.136 million on Wednesday to an anonymous bidder at Sotheby's in New York, a record for a US artist at auction, the auction house said.
The price was below the $10 million to $15 million pre-sale estimate. A second portrait of Washington failed to sell, a Sotheby's spokesman said.
The portraits on sale on Wednesday were among a group of works being sold by the New York Public Library to raise money for books and other materials.
Stuart is known for his portraits of the first US president, one of which hangs in the East Room of the White House. An unfinished Stuart portrait of Washington appears on the $1 bill.
Thirteen of the 16 available lots, representing 15 of 18 works, sold for a combined $15.64 million, Sotheby's said. The pre-auction estimate for all of the works was $22 million to $31 million.
The portrait depicts Washington in his last year of office, seated and wearing a black velvet suit, holding a document and with a sword resting on his lap. The seascape in the background refers to Hamilton's actions to boost trade and commerce and help create the US Navy.