So lets just say I reach the end of the cdt northbound and I decide to keep going into canada's great divide trail. Would that be bad news without a passport or could I manage to sneak in and stay out of trouble through my canadian journeys? From what I understand you only need a passport to get back into the US but I would assume that's if you were traveling by car or airport anyway. I've never stepped foot outside my region so I have no idea how it would work.