South Fork Snake River

The Fall River is the largest tributary of the Henry's Fork, a runoff-fed freestone that tumbles off the Pitchstone Plateau in southwest Yellowstone, past a string of waterfalls, and out onto the potato ground east of Ashton. It fishes late — high and off-color into June, then a July salmonfly-to-PMD dry-fly river most Henry's Fork anglers drive right past.

The Henry's Fork is the spring-fed tailwater that runs from Henrys Lake through Island Park and on to its confluence with the South Fork Snake near Rexburg. The slow flat water of Harriman State Park (the Railroad Ranch) is the most famous technical dry-fly stretch in the West.

The Idaho Teton is a low-gradient, spring-influenced meadow river winding through Teton Valley between Victor and Driggs, with the Teton Range on the eastern skyline. It fishes like a big spring creek for native Yellowstone cutthroat that rise honestly to a good drift, then drops into a hazardous whitewater canyon that holds the biggest fish before spreading through farmland toward St. Anthony.

A high-desert freestone under the Pioneer and White Knob ranges that turns, below Mackay Reservoir, into a short cold tailwater growing wild rainbows past 20 inches — then spreads out below Arco and sinks into the desert at the Big Lost Sinks without ever reaching the sea.

The freestone that runs down the spine of the Wood River Valley past Ketchum, Sun Valley, Hailey, and Bellevue — a wild, unstocked river of heavily spotted rainbows and thick lower-river browns, best fished on foot with a dry-dropper once July runoff clears.

The rare trout tailwater you can fish on a lunch break — cold, clear water off the bottom of Lucky Peak Dam runs straight through downtown Boise, paralleled the whole way by the paved Greenbelt. Wild brown and rainbow trout (browns commonly 16-20 inches), native redband, and abundant mountain whitefish. Flood-control and irrigation releases dominate: summer often pushes 1,000-7,000+ CFS and fishes poorly, but the river turns on after irrigation season ends in fall and through winter at a wadeable 150-600 CFS.

A big, cold, low-elevation river that draws anglers from all over for one thing: B-run steelhead — the largest summer-run steelhead south of the Canadian border, ocean-going rainbows that average 10-13 pounds and push past 20. It's classic spey country, swung flies on broad even-depthed runs from Lewiston up through Peck and Lenore, with a shoulder-season dry-fly window for native westslope cutthroat and rainbows when the main stem drops and cools.

A wild, unstocked freestone that runs right along US-12 for 70 miles of clear-water pocket water — native westslope cutthroat that eat dries two steps from the pullout, plus bull trout in the deep holes. Snowmelt-driven and treacherous to wade; it's a walk-and-wade river, not a trout float, and rarely comes into shape before mid-July.

A hundred miles of roadless westslope cutthroat water running through the heart of the Frank Church–River of No Return Wilderness. Access is a five- to six-day float on a private lottery permit or an outfitted trip; the reward is eager dry-fly cutthroat protected as catch-and-release with single barbless hooks since 1973.