In doing research recently, I've run into the same circumstance over and over again: American families crossing the Canadian border, or vice-versa. If you've been raised in New England, it's not something you necessarily expect. We have a mentality that all New Englanders were Puritan settlers who remained here from their first settlement.
That's not always true. Families from northern New England or eastern Canada migrated across the border in search of new jobs or new opportunities. They may have stayed for years or just months. Sometimes their descendants forgot that they were anything but American.
Why do I raise the issue? Simply to challenge how you think your research. It's very easy to fall into a pattern of just looking for records in one area. If we assume a family was from Maine, we tend to focus on our work there. By doing so, we may miss the ancestor's actual records, just over the border in Canada. Always do an open-ended search - just in case!