ME
Nowhere in the park. Rule 4.1 covers the whole 200,000+ acres with no area, seasonal or day-use exception — the Perimeter/Tote Road, all gatehouses, campgrounds and day-use parking are inside the Park boundary, so there is no lawful place to park with a dog in the vehicle either. The rules text contains no written service-animal or ADA clause and the park's accessibility page does not mention service animals, so anyone travelling with a service animal should call Park HQ (207-723-5140) in advance rather than rely on a website. Nearest dog-legal big-country alternative: Katahdin Woods and Waters National Monument, where NPS allows leashed pets ("all pets must be kept on a leash no longer than 6 feet (2 m) at all times").
Managed by Baxter State Park Authority (governed by Governor Baxter's Deed of Trust; not the Maine state park system). Official pet policy. Checked against that page in August 2026.
We publish this because finding out at the trailhead is worse than finding out here. Rules change — check before a long drive.