National Parks
National Monuments
National Historical Parks, Memorials, and Battlefields
National Recreation Areas, Seashores and Trails
Other Preserves and Protected Areas
... 25 to 44, 21.9% from 45 to 64, and 16.9% who are 65 years of age or older. The median age is 39 years. For every 100 females there are 113.3 males. For every 100 females ...