The American Southwest is honeycombed with ruins from long-past civilizations. Mesa Verde National Park and Canyon de Chelly National Monument are well-known for their cliff dwellings, while at Bandelier National Monument the sandstone walls are pocked with "cavates" used as shelter centuries ago.

My first visit to Yosemite National Park back in June 1999 coincided with a rockfall that forced me out of a tent cabin in Curry Village and into one in Tuolumne Meadows. Ever since, I've been intrigued by rockfalls in the park's iconic valley. While the frequency of rockfalls in recent years might be alarming to park visitors, they are calling cards evidencing the active geology that's ongoing in Yosemite.

In Great Smoky Mountains National Park, every trail has a history. That’s what makes hiking here so fascinating. But no trail is as historic or as controversial as the Lake Shore Trail, which skirts Fontana Lake in North Carolina. The issue surrounding it is currently the longest-running open item on the park's agenda, but there’s hope it will be resolved soon.

John Muir long has been closely associated with nature and the national parks, and rightly so. If you admire him and his writings, let us point you to a site where you can peruse thousands of his letters, sketches, photos and journals.