While it's relatively well-known that pot farms have been planted in the backcountry of such Western parks as Sequoia and Yosemite, a similar problem is being confronted back East in Mammoth Cave National Park. To battle the problem, the park is offering a reward of up to $1,000 for information that leads to a successful prosecution of those growing the marijuana patches.

ReserveAmerica, the company that manages camping reservations for the National Park System and other federal agencies, can't seem to find a national park campground it likes. In listing its "Top 100 Family Campgrounds," the company doesn't cite a single national park campground.

With the high heat of summer setting in over Joshua Tree National Park, officials are closing some of their campgrounds for the coming months due to the usual lack of campers.