Except in easily identifiable cases like Colorado, Wyoming, etc., I
don't know how you would determine northeasternness, northwesternness,
etc. The coordinate system doesn't really support it.
As for US and Canadian "extreme points", I have a pretty complete list
of "dry" extremities at
http://www.bjbsoftware.com/corners/news_extemities.html and have
visited the ones highlighted in yellow on that page. Most of those
have photos and maps.
By the way, I think the easternmost point in the US and Maine is just
east of Quoddy Head on Sail Rock (photo available via link cited above).
BJB
> I presume that a definitive list of such places exists somewhere...
>
> Thanks,
>
> -- Frank