National Parks
National Monuments
National Historical Parks, Memorials, and Battlefields
National Recreation Areas, Seashores and Trails
Other Preserves and Protected Areas
... under the age of 18, 6.3% from 18 to 24, 31.0% from 25 to 44, 26.9% from 45 to 64, and 13.5% who are 65 years of age or older. The median age is 40 years. For every 100 ...