George Washington's personal copy of the US constitution has sold for almost $10m, Christie's auction house says.
The book, with the first president's own annotations, was printed in 1789 - his first year in office.
It had an estimated price of $2m (£1.3m) to $3m but bidding boosted the price of the 223-year-old book.
Historians say Washington's notes are what make the book so valuable, as the president was keenly aware of the precedents he would set in office.
The leather-bound book is described as in nearly pristine condition and is stamped with the Washington family crest.
It also contains the first acts of Congress, which included legislation to establish state, judiciary, defence and treasury departments of government.
The book was fought over between two bidders who remained anonymous during the auction. The new owner is the Mount Vernon Ladies' Association, which paid a final price of $9,826,500, Christie's later revealed.
"It's an exciting day. We are thrilled to be able to bring this extraordinary book back to Mount Vernon where it belongs," spokeswoman Ann Bookout told reporters.
The private, non-profit group, owns and maintains Mount Vernon, Washington's historic Virginia estate, and has said the book will become part of a new presidential library due to open in 2013.
The book was bound especially for the president by Thomas Allen, a New York bookbinder. He also created similar copies for Thomas Jefferson, the first secretary of state, and Attorney General John Jay.
The book sold by Christie's on Friday had been in the library at Mount Vernon for many years after Washington's death.
In 1876 it was sold at auction to a private collection, and was sold again in 1964 to Richard Dietrich, a notable collector of early Americana.
George Washington acted as commander in chief of the Continental Army in the War of Independence and was later unanimously elected as the first president of the US .
After serving two terms as president, he spent three years in retirement at Mount Vernon before he died in 1799.