The Bighorn River stands as one of the premier tailwater fisheries in the American West, consistently ranked among the top fly fishing destinations in the lower 48 states. Fed by the cold, clear waters of Bighorn Lake through Afterbay Dam near Fort Smith in southeastern Montana, this tailwater maintains ideal temperatures year-round, supporting fish populations that defy imagination — estimates place brown and rainbow trout densities at 3,000 to 5,000 fish per mile in the prime section below the dam.
The most celebrated stretch runs from Afterbay Dam downstream 13 miles to the Bighorn Access Site, carving through the rugged landscape of the Crow Indian Reservation. The river flows clear and cold throughout the year, making it one of the few Montana rivers fishable even in winter. Access is limited due to Crow Tribal and private land ownership, but the National Park Service and State of Montana maintain public launch facilities at Afterbay Dam, the 3-Mile Island (Lind) access, and the Bighorn Access Site.
Most anglers float this section in drift boats, stopping at likely spots along the way. The Bighorn exceptional visibility allows sight-fishing opportunities rarely matched in the region. During peak hatches, 10 to 20 rising fish within easy casting distance simultaneously is not uncommon — a sight that reduces even seasoned anglers to trembling wrecks.
The hatch calendar is rich and predictable. Midges and scuds (freshwater shrimp) are the backbone of the fishery year-round. The Pale Morning Dun emergence — typically late June through August — is the headline event. Fish #16-18 Sparkle Duns and PMD Cripples during early afternoon hours. August marks the transition when the evening caddis hatch fires up in earnest; a tan or Elk Hair Caddis in #14-16 during golden hour produces explosive surface action. Blue-winged Olives dominate fall and winter, offering outstanding dry fly fishing on overcast days.
For nymph fishermen, scuds in pink, tan, and olive are the most productive patterns. San Juan Worms, Pheasant Tail nymphs, Hare Ears, and Zug Bugs round out a complete nymph box. In winter, Bighorn Specials, Woolly Buggers, and Muddler Minnows draw out the largest fish on streamer swings.
Gear up with a 9-foot 5-weight for dry flies and small nymphs, stepping to a 6-weight sink tip for streamer work. Tippet runs fine here — plan on 4X to 6X for most presentations. The Bighorn rewards precise, drag-free drifts and punishes sloppy casts. Learn to mend aggressively and the fish will find you.
Fort Smith serves as home base, with Bighorn Fly and Tackle and Bighorn Angler providing current conditions, guided trips, and local intel. The nearest major airport is Billings Logan International, roughly 75 minutes from Fort Smith via I-90 East and Highway 313. This is bucket-list water — plan accordingly.
