There are four Settlements in New Harbor, 2-4 can be missed if you progress too far in the Main story and choose certain Options
[1] Longfellow's Cabin: After arriving in Far Harbor, you’ll be directed to Old Longfellow to reach Acadia. Go with Old Longfellow to Acadia during the Walk in the Park quest to unlock this workshop.
[2] Dalton’s Farm: Speak with Cassie in Far Harbor and complete the Blood Tide optional questline to gain workshop access to Dalton’s Farm.
[3] National Park Visitor'a Center: Speak with the Bartender in Far Harbor and complete the Quests Rite of Passage + The Hold Out to unlock this Settlement
[4] Echo Lake Lumber: Complete the quest Rite of Passage and start the quest Turn Back the Fog from Small Bertha in Far Harbor. Refuse to let Malcolm have the land to take it for yourself.