The recent article about the roughly 30 designations that are in play across the 391 units of the National Park System highlights just one of the disparities that exist among units. Another example is the uneven quality of the 391 units' websites.

Early visitors to Yellowstone National Park didn't travel lightly, as this video shows. They seemed to cram everything they could into their trailers and head off, ever-hopeful that their rigs could stand the demands of the uphills and downhills.

Navajo National Monument includes great history, fine scenery and an off-the-beaten-path location that allows you to escape the crowds. The park also includes an interesting wildlife species—a carnivorous mouse with a call said to resemble the howl of a wolf.

The Pacific Crest Trail ranges from Canada to Mexico, running through Washington, Oregon, and California along the way, traversing not one but seven units of the National Park System in the process. While mountain bikers are not supposed to use the trail, recently some have been poaching sections in California.