At the northern end of US Route 1 in Fort Kent, ME
See southern end

Since I've now been to both the northern and southern ends of US 1, my life goals are fulfilled!  Is it possible that there can be any further purpose for my life?

This is the border crossing to Canada.  The road here is apparently not actually US Route 1, which technically ends a couple of hundred feet to the right.
This is not my picture, but from  www.corvettesconquercancer.com/ ft__kent.htm taken 2 years later.  My picture didn't turn out, possibly because we were in a real hurry to get back down south -- it taking much longer to get here than we anticipated.  (By the way, be sure to get gasoline in Fort Kent before heading south to Medway, ME.  There are many miles of nothingness if you go via Maine Route 11, as we did.

This is the Clair, NB to Fort Kent, ME bridge.  I believe Fort Kent is to the right.  The river is the St. John, which forms much of the northeastern and eastern border of Maine with New Brunswick.  It is flowing north at this particular point.  The picture is from http://www.tc.gc.ca/programs/surface/bridges/claire.htm