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, 6.7% from 18 to 24, 33.6% from 25 to 44, 20.6% from 45 to 64, and 9.6% who are 65 years of age or older. The median age is 35 years. For every 100 ...