A Boundry Line Post between Canada and United States

Undivided back, looks to be a U.S. card addressed to David Merrill, Chester Depot, Vermont, care of Aunt Emily from A.W. Davis. Dated June 15, 1908. Shows a boundary marker.

The "Treaty of Washington" refers to the Webster-Ashburton Treaty of 1842 (as far as I can tell) and this would therefore be somewhere along the border of Maine with what is now Canada, as that contentious issue was what the Treaty settled.