The Pacific Crest Trail zigzags some 2,650 miles from Mexico to Canada . It cuts through seven national Parks and 24 national forests as it travels through California, Oregon and Washington. Its a trail of ever-changing obstacles - from some of the highest mountain passes in the west to the hottest desert in the country. The two to three hundred hikers who attempt the PCT each year often find out quickly if they have what it takes for the journey ahead.

Far in the Pacific, 250 miles from Honolulu, a hidden wilderness teems with life ... the Northwestern Hawaiian Islands. In 2006, the islands were declared a national monument, in large part because of the area's more than 7,000 marine species. In this special, come aboard a voyage led by scientists from the National Oceanic and Atmospheric Administration who are researching disease-plagued coral reefs, endangered monk seals and the millions of birds nesting in the volcanic islands and atolls.

The stark appearance of Canyonlands conceals life in unexpected places.

A new wilderness emerges in Glacier National Park as the ice melts.

Join National Geographic as we trek between low and high country to experience big game deep in the taiga forest, beautiful subarctic vistas of the tundra, and the challenge of ascending to the top of North America.