Box Canyon is the legendary stretch of the Henry's Fork of the Snake River just below Island Park Reservoir, a fast, deep, rock-walled canyon in eastern Idaho that ranks among the most storied trout water in North America. Roughly three and a half miles long, it's a place fly anglers travel across the country to fish, famous for the big, powerful rainbow trout that hold in its heavy current. Set at about 6,300 feet in the Caribou-Targhee National Forest near Island Park, some 28 miles south of West Yellowstone, it pairs world-class fishing with a rim-top campground and canyon views that stand on their own.

The fishing is the main event and it has a distinct character. Unlike the placid, glassy meadow water the Henry's Fork is also known for, Box Canyon is fast, broad and pushy, and it fishes primarily as nymphing water thanks to an enormous food supply dominated by stonefly nymphs. This is a catch-and-release section, and regulations call for artificial lures and flies with a single barbless hook. The reward for the effort and the wading is a genuine shot at the kind of rainbow that makes the whole trip worth it.

Box Canyon Campground sits right on the rim above the river, one mile south of the Island Park Ranger Station off U.S. Highway 20. It's a small, pleasantly rustic operation: 18 first-come, first-served tent and RV sites run by a concessionaire, shaded by lodgepole pine and Douglas-fir near the canyon edge, with two vault toilets, water hydrants and a bear-proof dumpster. It typically operates from late May into early September, and because sites aren't reservable, arriving early in the day pays off during peak summer.

You don't have to fish to enjoy it. A three-mile trail traces the canyon rim from the campground, delivering scenic overlooks that hikers and photographers love, with shorter spur paths dropping down to the river for casting or simply sitting by fast water. Wildlife is abundant in this corner of the Island Park country, moose especially, and the bear-proof dumpster is a reminder to store food properly.

The river here is swift, cold and deceptively strong, and the descent to the water is steep in places, so wading demands real care, good boots and honest judgment about the current. At 6,300 feet the nights run cold even in midsummer, and the season is short. Come with layers, bug spray, sturdy footwear, and a fishing license if you plan to cast. Between a bucket-list trout fishery, a rim-side campsite under the pines, and a canyon trail with a view, Box Canyon is one of eastern Idaho's true treasures.