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 connects California to Oregon and Washington. It’s 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 thru-hikers who attempt the PCT each year find out quickly if they have what it takes for the journey ahead.

America’s Wild Spaces takes you on an epic journey following just a few of these hikers as they test their mettle. The five sections of the Pacific Crest Trail each present a new and daunting obstacle:

Southern California:
The Pacific Crest trailhead lies just feet from the Mexican border. Our journey starts here, with ultralight thru-hiker Monty Tam. Here water is in charge, and some days that means walking up to 20 miles between fill-ups.

Central California:
The end of the desert marks the beginning of another, elevated challenge: the Sierra Nevada. Hikers transition at Kennedy Meadows General Store. We’ll tip the scale to meet Denise Park. She’s got one of the heaviest packs on the trail—but does she have the heart to carry it?

Northern California:
Here the High Sierra yields to the volcanic Cascades. No one knows that more than geologists Greg Hummel and Paul Hacker. They met on the trail while thru-hiking over 30 years ago. Now they’re back to check out some of the geology they missed on their journey.

Oregon:
By now, hikers have completed over 1,700 miles of California trail. It’s taken them around three months to get here, and the work of about 1,000 volunteers annually to make that possible. Today those volunteers are mules, hauling heavy gear into the backcountry. They’re not the only equines out here. Janice Raddatz and her horses Jur and Harmony are here too, pushing northward.

Washington:
The trail finally ends past the spectacular Cascades National Park, at the Canadian border. Find out who made the distance and how the trail has changed them.

As it winds through California, Oregon and Washington, the Pacific Crest Trail changes with each step, and each step changes those who challenge it. Have you hiked the Pacific Crest Trail? Comment to share your trail stories. And don’t miss America’s Wild Spaces: Pacific Crest Trail, Wednesday, August 8th at 7P et/pt on Nat Geo WILD.