The ten essentials, unchanged
Navigation (map + compass — phones fail at canyons), sun protection, insulation, headlamp, first aid, fire, repair kit, food, water + filtration, emergency shelter. The list is 80 years old and still correct — the phone-based shortcuts fail precisely where the park is best (deep canyons, above treeline).
Park-specific additions
Desert parks: 2–4 liters per person per hike, electrolytes, and a hat that shades the neck. Alpine parks: rain shell (afternoon storms), layers for 30°F swings, and altitude awareness. Wildlife country: bear spray (Glacier, Yellowstone backcountry) and the food-storage rules the signs repeat.
The regrets list
The items visitors regret skipping: the paper map (cell service lies), the extra socks, the headlamp (the sunset hike that ran late), and the shuttle schedule photo. The items visitors regret bringing: the drone (banned everywhere), the dog on non-pet trails, and the third lens for photography that never happened.