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It was tricky to find any information on this campsite and then the loop road didn't open until just before I left the Millinocket area. It has been a very wet spring after a heavy winter, so there were lots of delays and it didn't' open until after Memorial Day, so I didn't get to stay here, but I did get to visit!
Because the Katahdin Woods and Waters (KWW) National Monument is so new, information and services are limited. Sometime this summer they are supposed to erect signs to the park; until them you're dependent on small signs and trusting you haven't missed a turn.
On to the campsite…it's first come, first served, at the beginning of the gravel loop road in the southern section of KWW. There are picnic tables, vault toilet, fire ring, and a tent pad. To light a fire, you will need a fire permit. Per their website, "A free permit is easily acquired prior to a visit by calling the Northern Regional Office of the Maine Fire Service at 207 435-7963 or visiting them at 45 Radar Street in Ashland, Maine." It's bear country, so plan appropriately. There's a spot with easy access to the pond/stream for launching a kayak (I"m not sure how deep it is, esp mid-summer) or wildlife watching (moose, bear, birds).
The 17-mile loop road features overlooks that include views of Mt. Katahdin, trails to peaks and waterfalls, and multi-use trails for bicycles, horses. There's an information board here as well.
You'll want to pick up any necessary items and fuel in Millinocket before you head into the Monument. Don't count on cell service. Be prepared to change a flat tire.
To get information about KWW, you MAY be able to visit the visitor's center in Millinocket (it was only open 1-4pm on Thursday; it has longer hours during the summer), but I found the best source was a Friends of KWW booklet that I picked up at a Maine Visitor's Center that included a map centerfold. There's a map here, too: Katahdin Woods and Waters Map