Some of what appears in this series on Yellowstone National Park is taken from our book Montana's Yellowstone River: From the Teton Wilderness to the Missouri.

Along with geysers, hot springs, mud pots and fumaroles, the magnificent Yellowstone River is a major centerpiece of our Yellowstone National Park. What this fabled river brings to the Park is pertinent to an understanding of how important the Yellowstone River is to its host.

Just off the Continental Divide, deep in Wyoming's Absaroka Range and Teton Wilderness, Younts Peak brushes thin air at 12,156 feet. When the melt season arrives, snowfields in a cirque high up on the massif's north face and its other flanks are adorned with countless rivulets.

Trickling off the crusted snow, they weave in and out of the mountain's tundra forming into small creeks as they gather in the denser vegetation below, providing the initial waters for the North and South forks of the Yellowstone River. Beneath Younts' west wall, the two branches unite to power the surge of the largest undammed, free-running river in America as it commences its 670-mile long odyssey to meet the Missouri beyond Sidney, Montana. And what a journey it makes!

From its spawning grounds 28 air miles below Yellowstone National Park's southeast corner, the legendary river enters a narrow, deep canyon where it fights its way down a boulder-strewn course. For about 10 miles, the newly formed river passes through a forest of pine, spruce and fir fitted with small meadows and willow flats.

Here the river - beautiful, untamed and gaining its wild soul - is connecting with some of the nation's finest wilderness landscape. Far from any road, this is the gorge of the Upper Yellowstone and a place where the majestic river is preparing to enter the nation's grandest national park.

Near Castle Creek, the Yellowstone departs its canyon confines and embarks on a torturous meander through marshy river bottoms of the twenty-one-mile long Yellowstone Meadows and Thorofare Valley. These wetlands extend from one to two miles across and the river with its islands, channels and deep pools is up to 160 feet wide in places.

Lush meadows of high grass and dense willows border provide prime moose habitat as well as a summer home for the Northern Yellowstone and Jackson Hole elk herds. Cutthroat trout move upriver to spawn here in early summer attracting the king of the wilderness... the silvertip grizzly bear.

Other wildlife - bison, eagles, bighorn sheep, cougars and deer - are plentiful. Canada geese and sandhill cranes call out early in the morning throughout the summer and the Delta pack of the Yellowstone wolves has taken up territory here.

The trail coming from the river's headwaters and Marston Pass on the Continental Divide intersects with several other routes near Bridger Lake and Thorofare Creek. Here the Thorofare Trail takes over and heads towards Yellowstone Lake skirting and passing through the meadow's east perimeter. Fording some of the peripheral streams, especially Thorofare Creek can be tricky business.

The water in these wildlands is swift, deep and cold. High runoff and lasting snowbanks make much of it impassable until mid-July... just part of the great wilderness experience this first segment of the Yellowstone River offers.

While the bottomlands the Yellowstone River occupies are spacious, the mountains on either side reaching high above them continue to be impressive. Some of the views, especially from vantage points such Hawk's Rest, about two miles south of the park boundary, combining panoramas of the river and its lofty guardians are almost unbelievable. Wyoming's 80-mile long Absaroka Range with its 10,000 to 11,000-foot summits, including the Park's highest point - 11,358-foot Eagle Peak - form a fortress on the river's sunrise side.

Early explorers who entered this wonderland called the Absarokas "Yellowstone Mountains" and "Great Yellowstone Range." Since these mountains had been part of the Crow Indian Nation ancestral lands, in 1885, the US Geological Survey maps gave them the moniker the Crow used to describe themselves... Absaroka meaning "children of the large beaked bird."

The Continental Divide, passing through the Absaroka Mountains, presides over the Yellowstone River's west side in its upper course. As the Divide snakes northwest it loses elevation and crosses Two Ocean Pass, an almost flat area with plenty of water. Here North and South Two Ocean creeks meet and part.

One fork becomes Atlantic Creek and makes its way to the Yellowstone River, while the other drains towards the west and the Snake River. Massive Two Ocean Plateau, reaching 10,115 feet at its highest mark, now carries the Divide. The Plateau drops off to Yellowstone Lake on the north while the Continental Divide climbs to the heights west of the lake.

Rick and Susie Graetz are from Helena and are authors, photographers and publishers.