My first trip to the famed Henry’s Fork was the year Yellowstone National Park was ablaze (1988), and I could not fish my beloved Firehole River.  Out of desperation, I started seeking alternative fishing, and the first place to come to mind was Snake River and Henry’s Fork, the Railroad Ranch/Harriman Ranch area in particular (now known as Harriman State Park).  I had wanted to fish Henry's Fork for many years, but could not get away from the beloved Firehole. 

The fly fishing masters of the past have all “passed this way.”  The wading is easy, but getting a fish in is a challenge.  This is a “push no waves as you wade” the area!  It takes cautious fishing, and drag-free presentations.  Eighteen inch leaders of 5x to 7x work very well.  This is dry fly water!  It is not “creel filling” fishing – it is mirror clean spring creek water much of the time and a few big ones (over 18 inches) are considered a good half day work.  The water quietly flows by with pea-gravel channels separating the aquatic growth.  Several hatches can be coming off at once.  It is exciting to watch the caddis flies rise from the grassy banks late in the evening and the fish begin to rise like a drops of spring rain descending upon a river. 

Henry’s Fork Anglers http://www.henrysforkanglers.com/guideservice/  is one well known guide services, though there now are a number of fine guides available.  “Hyde Outfitters is a full guide service, fishing lodge and fly shop located in Southeastern Idaho. Hyde's Last Chance Lodge is within walking distance of the Henry's Fork and just 30 miles south of West Yellowstone Park placing you in an ideal location to fish some of the Rocky Mountains best-- including the Teton, Beaverhead, the South Fork of the Snake, Silver creek and the Madison River. Ask the fly shop staff what's working best, grab some dinner and settle in to a variety of accommodations from suites to single rooms”

http://www.flyfishingconnection.com/guideshenryfork.html  

Some other listings are:

http://www.westyellowstonenet.com/fishing/fly_fishing_guides.php The Harriman Ranch is as captivating and technical a stretch of water as you will find anywhere in the world.  Many a well-ll-traveled fisherman has settled down here to spend the vast majority of his remaining angling days stalking the large, wary rainbows with which this section of river has become synonymous. Nearly all of this area is very easily waded and its openness affords unobstructed casting. The slow water stretches of the Henry's Fork are so rich in quantity and diversity of aquatic insect life that the trout need not be opportunistic. Instead resident Rainbows have the luxury of much more food passing by them than they could possibly ingest. A fish that eats an infinitesimal percentage of the natural insects it sees is a very difficult one to coax to an artificial offering. To complicate matters, several different insect hatches often occur simultaneously. Individual fish, in turn, key in on specific life stages of specific species of insects. Proper fly selection, based on careful observation, is critical. Approaching this stretch with reverence, a degree of humility, and tempered expectations can result in priceless memories. Enjoy the pristine surroundings, test your skills, and savor your victories. You will be glad that you did.”  http://www.westyellowstonenet.com/fishing/henrys_fork.php

If you are interested in a “classy place to stay,” while fishing the area, you won’t be disappointed in the Angler’s Lodge 

Flies to use:

April-May:         Iron Blue Quills

May-June:          Salmon flies, Western green drakes, PMD, Brown drakes, olive caddis, and golden stoneflies.

July:                       Small Blue Quills, Small western drakes, PMD, Light Cahills, Speckled duns, Ants, Caddis.

September-October:  Caddis, dark midges, Iron Blue Quills, Mahogany Duns

Tight lines and happy fishing.