A letter written by President Thomas Jefferson is valued at $500,000-700,000 ahead of Sotheby's Fine Books and Manuscripts Sale in New York on December 5.
Jefferson wrote the letter, dated June 20, 1805, to Dr William Eustis of Massachusetts - a former senator who would become secretary of war in 1809.
The first half of the letter references the newly created state of Michigan and the decline of federalism in New England.
The second half of the letter, however, goes on to reference the Lewis and Clarke expedition - the most important exploration of the American interior ever undertaken and one of the most enduring legacies of Jefferson's presidency.
The letter relates the imminent arrival of a delegation of Native American diplomats from the newly discovered territories, stating: "I have the pleasure to inform you that one of Capt Lewis's barges returned to St. Louis brings us certain information from him.
"He has sent in his barge 45 deputies from 6 of the principal nations in that quarter … we shall endeavour to get them to go on as far North as Boston, being desirous of impressing them correctly as to our strength & resources.
"This with kind usage, and a commerce advantageous to them, & not losing to us, will better secure their & our peace & friendship than an army of thousands."
This is one of just two letters by Jefferson referencing the expedition to come to auction in over 60 years.
The other set an auction record for the president, selling for $1.4m at Sotheby's New York in 2002.
We have this 1848 Peter Force printing of the Declaration of Independence, famously drafted by Thomas Jefferson.
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