Cape Cod National Seashore
Annual visitors: 4.5 million
Location: Wellfleet, Mass.
Size: 68 square miles
Founded: 1961
Highlights: This public beach has six swimming beaches, but it also has walking, hiking and biking trails, as well as cranberry bogs. This park has many free, ranger-guided activities, such as yoga on the beach, campfires, canoe trips and evening lectures.
