An act making Vermont the 14th state, signed by Thomas Jefferson, has achieved $32,500 at Swann Auction Galleries, beating an estimate of $25,000 by 30%.
The lot dates to February 17, 1791 and is one of 28 known copies to feature Jefferson's signature.
Vermont entered the Union in 1791 after splitting from New Hampshire and immediately renouncing slavery.
This led to concern in the South that the balance between pro and anti slavery states might be adversely affected. However, Kentucky's emancipation from Virginia in 1792 went some way towards calming the situation.
Jefferson's role in the foundation of America ensures a huge market for autographs and memorabilia. A key letter on the role of the American government sold for $250,000 at Profiles in History in 2012.
Another document relating to the founding of Vermont signed by John Hancock in 1779 made $25,000 against a $12,000 estimate (an increase of 108.3%).
Vermont declared its statehood in 1777, although it was not recognised officially until 1791.
The letter relates to attempts to mediate border disputes between the fledgling state and its neighbours New York, New Hampshire and Massachusetts.
John Hancock's large and distinctive signature on the US Constitution has become synonymous with a signature in America, making him one of the most recognisable founding fathers.
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