Lamar Valley from the Northeast Entrance Road
The Lamar rises in the Absaroka Range on the park's eastern edge and flows northwest about 40 miles, entirely inside Yellowstone, to the Yellowstone River. The Northeast Entrance Road between Tower Junction and Cooke City runs beside the river through the Lamar Valley, and the valley floor is the easy water: pullouts every few hundred yards, open meadow banks, riffles, boulders and undercut banks. The Lamar River Trail from the Soda Butte confluence area follows the river upstream on foot for anglers who want to leave the road. Expect bison on the banks and stay well back from them.
Lower canyon and the Yellowstone confluence
Below the valley and the Slough Creek junction the Lamar drops into a basalt canyon and meets the Yellowstone just east of Tower Junction, downstream of the Grand Canyon of the Yellowstone. The lower river is reached from the Northeast Entrance Road near the Lamar River bridge and the Yellowstone River picnic area, not from Tower Fall, which is on the Yellowstone several miles upstream of the confluence. This canyon water is more rugged than the valley and holds the river's rainbows and cutbows along with big cutthroat. Sections of the canyon have been closed for road reconstruction since the 2022 flood, so check park road status before you count on it.
Soda Butte Creek and Slough Creek
Soda Butte Creek enters from the northeast and the road to Cooke City follows it the whole way; the confluence with the Lamar is the most fished spot in the drainage. Slough Creek enters from the north below the valley, with its famous meadows reached from the Slough Creek campground road and the trail beyond it. Both carry the same Yellowstone cutthroat and the same rules as the Lamar, and both clear a little sooner than the main river after runoff.
Yellowstone cutthroat
Cutthroat are the park's only native trout and the Lamar drainage is one of their strongholds. They were never lost here; the park protects them by requiring release of every native fish and removal of the nonnatives. The river is in runoff when the park opens over Memorial Day weekend and usually does not come into shape until about the second week of July, then fishes through October with drakes, PMDs and caddis in July, gray and green drakes into early September, and hoppers from late July through September. Fall brings blue-winged olives and midges on calm days. Sight-fishing to rising fish beats blind casting on this river; be ready to walk to find them.
Season and regulations
No shop quotes a flow range for the Tower gauge, so the 150 to 600 cfs range this page compares against comes from the USGS long-term monthly medians at 06188000 for August through October (about 190 to 300 cfs) widened to take in the flows local shops have called good: Big Sky Anglers reported the river in excellent shape near 200 cfs in late August 2026 and Madison River Outfitters called it in very good shape at about 590 cfs in mid July 2024. The July median is over 1,000 cfs, which is runoff, and the river is not wadeable then.
A Yellowstone National Park fishing permit is required for anyone 16 and older; state licenses are not valid inside the park. In 2026 most park waters, the Lamar included, are open from the Saturday of Memorial Day weekend through October 31, sunrise to sunset. Only lead-free artificial flies and lures with barbless hooks are allowed, felt soles are banned, and all native fish must be released. The Lamar drainage, including Slough Creek and Soda Butte Creek, is inside the Native Trout Conservation Area: every rainbow trout, brook trout and identifiable cutthroat x rainbow hybrid you catch must be killed, and there is no possession limit on them. If you cannot tell, let it go. The park can close streams on short notice for low water or high temperatures, so read the current NPS fishing regulations before your first cast.