The Webster-Ashburton Treaty was signed August 9, 1842 between the United States and Great Britain to settle the eastern Canadian-U.S. boundary. The treaty was negotiated between Daniel Webster, Secretary of State under President John Tyler, and Lord Ashburton of Britain.

Webster, known during his life and to generations thereafter for his remarkable oratory, had few opportunities to show how well he could build for permanence, though the sure logical of his genius would seem to have adapted him peculiarly for such work. The Webster-Ashburton Treaty is considered his single greatest achievement, an arrangement which was entirely satisfactory to neither party, and was therefore probably as fair a compromise as could have been devised.