All Maine Residents receive free admission to Maine State Parks and Historic sites! No rain date. Free admission does not apply to: Acadia national Park, the Allagash Wilderness Waterway, Baxter State Park, Peacock Beach, ME Wildlife Park, Scarborough Beach State Park, Swan Island, the Penobscot River Corridor, or the Penobscot Narrows Observatory in Prospect, through admission to Fort Knox historic Site will be free that day.