National Parks
National Monuments
National Historical Parks, Memorials, and Battlefields
National Recreation Areas, Seashores and Trails
Other Preserves and Protected Areas
... of 18, 3.5% from 18 to 24, 22.3% from 25 to 44, 28.7% from 45 to 64, and 28.1% who are 65 years of age or older. The median age is 50 years. For every 100 females th ...