An autographed letter from George Washington is the headline lot of Swann Auction Galleries' May 22 sale in New York.
It carries an estimate of $20,000-30,000.
The document dates to December 26, 1777, a time when the bulk of the continental army was garrisoned at Valley Forge near Philadelphia.
It's addressed to president of congress Henry Laurens and relates to an internal ranking dispute between officers.
Washington asks Laurens to hold off on a decision until "Congress may be fully possessed of the subject and apprized of the difficulties involved in matters of this sort."
A letter written by Abraham Lincoln to George W Rives, a Whig activist, in 1849 is estimated to make $15,000-20,000.
Rives had asked Lincoln for his recommendation for a post in Minnesota.
The future president had just returned to his law firm in Illinois after a one year term in the house of representatives and writes: "You overrate my capacity to serve you.
"Not one man recommended by me has yet been appointed to any thing, little or big, except a few who had no opposition.
"Besides this, at the very inaug[u]ration I commenced trying to get a Min[n]esota appointment for Dr. Henry, and have not yet succeeded; and I would not now, lessen his chance, by recommending any living man for any thing in that Territory".
Interested in collecting? Sign up here for our free newsletter and get the latest news direct to your inbox.