If you're hiking the island's trails, you can camp at one of the five spectacular sites here (each has a lean-to shelter and sparkling views of Isle au Haut Bay). The National Park Service (NPS) maintains the campground and reservations are mandatory. Applications open online on April 1 at 10am; all sites for the season are reserved within 30 minutes.
From mid-June through early October, the ferry to Isle au Haut stops at the Duck Harbor Boat Landing, near the campground. At other times, you'll have to disembark in town, and carry your gear the 4 miles to the campground. It has water and composting toilets. Bring food and all other essentials with you.