Acadia National Park protects the natural beauty of the highest rocky headlands along the Atlantic coastline of the United States, an abundance of habitats, and a rich cultural heritage. At 4 million visits a year, it’s one of the top 10 most-visited national parks in the United States. Visitors enjoy 27 miles of historic motor roads, 158 miles of hiking trails, and 45 miles of carriage roads. Size: 49,000 acres