This campground offers large sites, many with lean-tos and along the stream. a nice base for a morning ascent of Mt Katahdin. Black flies can be unbearable in May/June, so prepare accordingly. There are pit toilets. Bring either drinking water or a water filter for water from the stream. You'll need to bring all your supplies; there are no stores in the park, so stock up in Millinocket. Also, beware that you need to arrive no later than 8:30pm your first night! No cell phone coverage.
Baxter State Park is no frills, but great beauty. There are a few of New England's 4000-footers here, but the goal for most is Mt Katahdin, the northern terminus of the Appalachian Trail. If you stay here the night before, you can get an early start without having to wait at the park entrance. If you're not interested in the high peaks, there are trails along waterfalls and ponds, places to launch a canoe or kayak, ample opportunity to see moose.
2020, won't open until at least July. in 2019, it didn't open until late May because of a wet spring and trails were closed until mid-June because of snow cover on the trails.