They used to live over a much wider area of the island but the creeping irradiated fog has taken over much of it in recent years, and they’ve all been forced into Far Harbor. The human settlers in Far Harbor will be the first people you meet on the island. The Far Harbor Faction in Fallout 4 Far Harbor
It’s worth knowing that, if you’ve sided with the Institute or with The Brotherhood of Steel, you can call down either of these groups to wipe out the synths on the island, but then you won’t get their rewards. Each one has specific rewards and perks that come with helping them out, which is the sort of thing you should be used to by now. Fallout 4 Far Harbor introduces three new factions for you to juggle, although what happens with them won’t affect the rest of the game, so they’re more like mini factions.