Rising on the northeast slope of Joseph Peak in the northwest corner of Yellowstone Park the Gardiner River is born. The river starts at 10,000 feet. By the time it reaches the northwest corner of Gardner's Hole it has been joined by several other icy small streams. After it reaches Gardner's Hole, Fawn, Panther, Indian and Obsidian creeks join it. All are small, winding, willow lined, clear and cold, and all host numbers of brook and rainbow trout. The streams of Gardner's Hole are the only ones in the Park that may be fished with worms-but only by children twelve years and under.
Twenty miles from its source from where it passes under the Norris-Mammoth road bridge, there is a mile or so of very pleasant water. But proceed with caution as the walls of the canyon steadily constricts the river, bank fishing becomes tough and wading becomes risky. The river becomes a torrent and soon drops over 150 foot Osprey Falls, and the even steeper canyon below. It is dangerous to continue.
Hot spring runoff from Mammoth Hot Springs empty into Gardner at site called Boiling River. Here is evidence of Native American hunting/fishing camps. The canyon is thick with juniper, cottonwood, and Douglas-fir trees, and you might be lucky enough to see eagles, osprey, dippers, and kingfishers along the river and bighorn sheep in the steeper parts of the canyon. The area abounds with deer, elk, moose, waterfowl, beaver, squirrels, chipmunks and other small creatures, and birds. Opportunities for wildlife photos are everywhere. The area is scenic and the main road just a few hundred yards away.
Where the Boiling River converges with the Gardiner River there is a popular pool for the hot spring enthusiasts. Each Spring after run-off hot spring enthusiasts build a barrier of river rock to channel the ice cold Gardiner away from where the Boiling River merges with it. Enough of the Gardeners icy waters flow over the barrier to cool the water of the Boiling River whose water is, well, boiling hot. This is one of the few hot springs in Yellowstone where it is legal to swim in.
The Gardiner River returns to a more fishable although it is still swift, boulder-filled pocket water, and the fish, somewhat larger than above the upper Gardiner. The next approach to the river is a dirt road from a employee housing section for Park Headquarters at Mammoth. From the housing area road it is another half-mile before the stream comes into sight along the Mammoth-Gardiner road.
The five miles between Mammoth and Gardiner area are very pleasant miles to fish. There is just enough difficulty getting into and out of the stream, and in fishing it, to deter the casual fisherman. This is prolific piece of water for the proficient fly-fisherman.
On September 13, 1869 the Cook-Folsom-Peterson Expedition entered the park region and crossed the Gardiner River at its mouth on their way up the Yellowstone. On August 26, 1870 the Washburn-Langford-Doane Expedition entered what was to become the northern boundary of Yellowstone National Park at Gardiner MT and camped near the confluence of the Yellowstone River and the Gardiner River before they crossed the river and proceeded south up the Yellowstone River. Both these expeditions did not explore the Gardner and thus did not encounter the geothermal features of Mammoth Hot Springs. The 1871 Geological Survey of the park region by F. V. Hayden did explore the Gardner River Drainage.