Henrys Fork of the Snake River

There are few rivers that are more highly regarded to anglers as the Henrys Fork of the Snake River.  The Henrys Fork watershed covers a mind blowing 1.7 million acres and over 3000 miles of rivers & streams.  Quite impressive, but if you zoom into the Henrys Fork itself, it bubbles out of the ground at Big Springs (28 miles southwest from Yellowstone Park) and flows relatively south to the confluence with the South Fork of the Snake River.

 The Henrys Fork is a place where you can always catch a fish, always.”  Doug Gibson – Orvis Guide of the Year, Orvis Lifetime Achievement Award

Who is Henry?  

The Henrys Fork derives its name from Colonel Andrew Henry (1775-1832), an early fur trader and partner in the Missouri Fur Company. Henry first entered the Snake River plateau in 1810.  The next year he began exploring the Montana – Idaho wilderness and discovered Henrys Lake and built a trading post named Fort Henry on the upper Snake River, about five miles south of present day St. Anthony.

The Henrys Fork is a tremendous dry fly fishery loaded with many species of trout, large wild rainbows and the ever elusive brown. The river flows through gentle flowing ranch land, timber covered canyons, and spring creek like sections, with tributaries that are spectacular fisheries in their own right.

 Henrys Fork Boat Access Map

Sections of the Henry’s Fork

We typically break the Henry’s Fork into a few different sections.  Here are the sections with a Boat Access Map at the bottom.


Officially, the headwaters of the Henry’s Fork is located at Big Springs, it produces 120 million gallons of water each day.  There are sections that are closed to fishing, but, most anglers will fish around Mack’s Inn and Coffee Pot Rapids.

Box Canyon

Just below Island Park Dam starts the Box Canyon section, it ends in Last Chance just a few hundred yards away from our Island Park Fly Shop.  Box Canyon is narrow pine lined canyon that is littered with rocks.  It can go from 100 feet at the widest to about 50 feet at the narrowest sections.  Stoneflies, Caddis, Mayflies, Midges, Terrestrials and all kinds of streamers work in different times of the year.  Nymphing is the most popular and most effective technique in catching fish in Box Canyon.

Harriman Ranch – a.k.a. Railroad Ranch

There is 6 miles of river known as the Railroad Ranch or Harriman State Park in the Island Park area.  The Henrys fork slows way down into a wide open high-country meadow with the majestic Centennial Mountains to the northwest & the Teton Range peaking out to the southwest.

The setting is breathtaking, but the dry-fly fishing is what really makes this place special.  Let me just name a few hatches that are on the Railroad Ranch (as well as the rest of the Henrys Fork): Midges, Caddis, Golden Stones, Salmonflies,  Yellow Sallies, PMD’s, Mahogany Duns, Brown Drakes, Gray Drakes, Green Drakes, Speckled Spinners, BWO’s, Flavs, Tricos, Dragonflies, Damsels, Ants, Beetles, & Hoppers.  All of those in 5 months.

For those of you that care or just want to know a brief history of the name.  The land was owned by Union Pacific investors from 1902 until 1977, it’s main purpose was a cattle ranch and private getaway for the Harriman & Guggenheim families.  The Railroad Ranch, a total of 22 square miles, was donated for free to the State of Idaho & opened to the public in 1982.  Now you know why it’s called the Railroad Ranch.

Mesa Falls Byway – (the Canyon)

Fly Fishing the Mesa Falls Byway (Highway 47) is for you folks that want to try something different, explore, or just get away from the crowded sections in Island Park.  There are several wood roads that head west along the highway, meandering throughout Targhee National Park.  Osbourne to Riverside is a really fun section to float in a drift boat, but be aware that it’s really challenging (towards Riverside) for anyone on the oars.  You can hike down the canyon sections and fish the river in relative solitude, explore Mesa Falls, check out Warm River (a tributary of the Henrys Fork), then work your way to Warm River, then fish the amazing section down to Ashton.

The Lower 

Once we reach Ashton Reservoir the Henrys Fork flows through fertile farmlands with the Grand Tetons overlooking your every move.  Just a couple miles west of Ashton (E 1300 N) is the Ora Bridge Boat Access.  The Henrys Fork flows close to the road, so if you’re wading, it’s pretty easily accessible through Vernon, Chester, and on the way down to the Fun Farm Bridge.

  • TRR Guide Matt Stalnaker putting his client on a beautiful brown trout

Eastern Idaho Fishing Report 7/14/23

Henry's Fork: The current flows out of Island Park are 1,370 cfs. Flows have increased recently due to irrigation demand and may continue to increase with the rising temperatures and no rain in the

  • Richard Cashio fishing with Guide Troy Troutner

Eastern Idaho Fishing Report 6/30/23

Henry's Fork: The current flows out of Island Park are 643 cfs. The upper HF in the Box Canyon area has been tough fishing, nymphing is going to produce the best using rubber legs

  • Fairlee Frey brown trout Henry's Fork with guide Danny Lane

Eastern Idaho Fishing Report 6/16/23

Henry's Fork: The current flows out of Island Park are 819 cfs. The upper HF in the Box Canyon area has been tough fishing, nymphing is going to produce the best using rubber legs

  • Henry's Fork salmonfly eating Brown Logan Martindale

Eastern Idaho Fishing Report 6/2/23

Henry's Fork: The current flows out of Island Park are 1,140 cfs. We are seeing salmonflies flying on the Henry's Fork.  A dry dropper should produce fairly well. Henry's Fork salmonfly #4 as the