Claim: The Webster–Ashburton Treaty allowed Canada to complete construction of a partially finished fort on contested lands.
Evidence: Since "Fort Blunder"—an unnamed U.S. fort in what is now part of northeastern New York—had been constructed north of the actual 45th parallel, the United States wanted to follow the old survey line, and the Webster–Ashburton treaty incorporated this change, leaving the half-finished fort on U.S. soil. Following signing of the treaty, the U.S. resumed construction on the site. The new project replaced the aborted 1812-era construction with a massive third-system masonry fortification known as Fort Montgomery.