National Parks
National Monuments
National Historical Parks, Memorials, and Battlefields
National Recreation Areas, Seashores and Trails
Other Preserves and Protected Areas
... 45 to 64, and 13.5% who are 65 years of age or older. The median age is 40 years. For every 100 females there are 102.1 males. For every 100 females age 18 and over, ...