The original Ten Essentials list was assembled in the 1930s by The Mountaineers, a Seattle-based organization for climbers and outdoor adventurers. In 2003, the group's updated "systems" approach made its debut in its seminal text on climbing and outdoor exploration, Mountaineering: The Freedom of the Hills (The Mountaineers Books), now in its eighth edition.

Why create such a list? The book's editors explain: "The purpose of this list has always been to answer 2 basic questions: First, can you respond positively to an accident or emergency? Second, can you safely spend a night—or more—out?"

Packing these items whenever you step into the backcountry, even on day hikes, is a good habit to acquire. True, on a routine trip you may use only a few of them. Yet you'll probably never fully appreciate the value of the Ten Essentials until you really need one of them.

Classic Ten Essentials

1. Map
2. Compass
3. Sunglasses and sunscreen
4. Extra clothing
5. Headlamp/flashlight
6. First-aid supplies
7. Firestarter
8. Matches
9. Knife
10. Extra food

Updated Ten Essential "Systems"

1. Navigation (map and compass)
2. Sun protection (sunglasses and sunscreen)
3. Insulation (extra clothing)
4. Illumination (headlamp/flashlight)
5. First-aid supplies
6. Fire (waterproof matches/lighter/candles)
7. Repair kit and tools
8. Nutrition (extra food)
9. Hydration (extra water)
10. Emergency shelter