Here is a group to follow if your interested in running the St Croix International Waterway commision.
For those wondering it is the river that forms the US Canada border in New Brunswick and Maine, and if you want a campsite on the river it is the group you want to talk to.

web site
https://www.stcroix.org/?fbclid=IwAR0De ... a_igTmgWxE

Face Book
https://www.facebook.com/SCIWC

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Choosing to save a river is more often an act of passion than of careful calculation. You make the choice because the river has touched your life in an intimate and irreversible way, because you are unwilling to accept its loss. — (David Bolling, Ho

Also keep in mind that whatever side of the border you start on you have to camp and depart on the same side. Not an issue because there are lots of campsites.