North Haven is a year-round island community and summer colony located in Penobscot Bay , Maine , United States . The island is part of Knox County and lies roughly 12 miles offshore. As of the 2000 census, the town population was 381; during the summer months, the population swells into the thousands with visitors and second-home owners. Though the island is a popular destination, it provides few tourist amenities -- one inn, a grocery store, and two gift shops -- and is instead geared toward those who have vacation homes on the island. The island is accessed by three-times daily ferry service from Rockland, Maine , provided by the Maine State Ferry Service . North Haven is unusual among Maine island communities for offering a K-12 school (Maine's smallest), whereas most islands only have elementary schools and tuition their high school students to high schools on the mainland ( Vinalhaven and Islesboro are the only other islands to offer K-12 education).