There are national parks that focus on geology, that provide windows into ancient civilizations, and which honor westward expansion. So should one that preserves fossilized mammoth bones be added to the mix?

Military personnel, federal employees and elected officials take an oath of allegiance or oath of office, but during the American Revolution there was a lot at stake for those who promised "true allegiance to the United States of America"—in writing. One of those historic documents was recently donated to Valley Forge National Historical Park.

When was the last time you tail-gated before a symphony concert? You'll be able to do just that this June at Great Smoky Mountains National Park when the Knoxville Symphony Orchestra helps the park celebrate its 75th birthday.

How much have the national parks changed since you were a kid? Have they changed? When you return to a park that you haven't been to in decades, is it like returning to an old friend, or visiting someplace totally alien?