YELLOWSTONE A PRISTINE, UNCROWDED WILDERNESS FOR WINTER VISITORS.

Byline: Roy Harvey Chicago Tribune 

Winter is Yellowstone's longest season. And for the relatively few visitors who come then, it is the best.

In the mountainous northwest corner of Wyoming, with slivers extending into Idaho and Montana, Yellowstone National Park is one of the crown jewels of the National Park System. It has always been an experiment. Created in 1872 during the heyday of materialism's western expansion, the 3,500 square miles of wilderness has survived most of humanity's usually well-meaning efforts at intervention.

Every summer, nearly 3 million visitors endure traffic jams and long lines to visit what was the nation's - and world's - first national park.

But winter is another matter. During the official winter season, which lasts from mid-December to mid-March, the visitor count drops to around 100,000.

For good reasons. In winter, only the road linking the park's north and northeast entrances is open to traffic. The rest of the park - with most of its scenic attractions - is reachable only by snowmobile or snowcoach. And it's austere. With most of the park at an altitude of more than 7,000 feet, winter unofficially can last from October until almost June. Snows are packed hard, from five to six feet and deeper in the drift areas, and it can get incredibly cold. Plus it can be more expensive in winter (there's no camping; snowcoach transportation costs more than a private car).

Yet those few park personnel who remain - a mere 400 compared with the 3,000 on duty in the summer months - say this is their favorite time of year in the park. It has also become the favorite time for hardy travelers who want to see the park's wonders in a different light - and without the crowds.

My wife, Karen Engstrom, and I became part of the uncrowded crowd last winter, taking a Nordic Fox Ski Club trip with 30 other Chicagoans for nearly 10 days of cross-country skiing.

We wanted to see it - and ski it - while we could. In a few years, more stringent (but yet to be determined) limits will be imposed on the number of winter visitors.

After flying to Bozeman, Mont., we took a bus to Mammoth Hot Springs, just inside the park where the unplowed road into the interior begins. There, a snowcoach took us to our lodge near Old Faithful.

From the snowcoach (a converted van fitted with tractor treads and skis) we saw bighorn sheep, elk, eagles, hundreds and hundreds of bison, coyotes, flocks of golden eye ducks, stream-feeding dippers, trumpeter swans - and breathtaking panoramic views.

Home during our stay in Yellowstone was the Old Faithful Snow Lodge, with 140 rooms and cabins the only accommodations open during winter in the park's interior. (An additional 120 rooms are available at Mammoth Hot Springs Hotel.)

Other than the snowmobilers, most winter visitors to Yellowstone, like us, come to ski. The land offers some of nature's greatest majesty: the bluest of skies, mountain ridges and frozen lakes, pristine forests, backcountry trails of varied lengths and difficulty, all in a fragile, primordial, almost untouched wilderness.

The Old Faithful area has more than a dozen well-marked, cross-country trails, loops from three to 20 miles, labeled "easy" to "very difficult."

The schedule on one typical day: a 7 a.m. tour of fast skiers to Mystic Falls. A half-hour later, a smaller group went on a snowshoe trek above the hills of Old Faithful. Heading out at a more comfortable 9 a.m. was a more ambitious group for a ski trip up the rugged Mallard Lake Trail.

Beyond these scheduled activities, individuals and small groups of skiers explored park trails on their own. One day at Lone Star Geyser, nearly five miles south of Old Faithful, two of our small groups coalesced for lunch on spread-out snow blankets and waited in the falling snow for the geyser to erupt - which it does every three hours for a full 30 minutes.

In most volcanic regions of the world, the molten magma is about eight miles beneath the surface; in Yellowstone, it is little more than a mile underground. That makes the park home to 10,000 thermal features: bubbling white mud pots, steam vents, fumaroles, cauldrons, sulfur pools, brilliantly colored travertine springs and 300 explosive geysers.

In groups of varying size and skill, loaded down with backpacks weighing 10 to 20 pounds and stocked with food, water, extra clothing and survival gear, we skied or snowshoed the steep hills and trails. On one excursion, we watched trumpeter swans reach down into the steaming Firehole River with their long necks, skimming the bottom of the streams for food. We were careful to keep our distance from the foraging bison, elk and moose.

Or, for small fees, we took daylong snowcoach trips to remote scenic areas, our guides/drivers giving us well-informed winter information along the way.

Even in the more remote northwest portion of Yellowstone, where rangers have reintroduced wolves, no area of the park was off-limits to skiers.

After a day of skiing, we would assemble for dinner at Snow Lodge. Given that all supplies must be brought in by snowcoach, the meals were reasonably priced (averaging about $10) and reasonably gourmet.

Many of us tourist skiers were oblivious to the controversies swirling around Yellowstone. Evening nature talks by park staff avoided the issues that troubled them privately: the shooting of bison as they wander off park grounds; the nearby oil and gas explorations and mining that pollute streams and threaten park flora and fauna; the imperiled nature of plant species (an estimated 4,000 of the 20,000 plant species in Yellowstone are endangered); the dwindling habitat for grizzlies and other species; and the problems of pollution from cars and other vehicles.

Humans are used to affecting things. But most of us - as visitors - were at our best in Yellowstone when we didn't intervene, when we affected nothing, when we left no traces but footprints.

On location

For more information or reservations on Yellowstone National Park, write: TW Recreational Service, P.O. Box 165, Yellowstone National Park, Wyo. 82190-0165. Or call [phone].

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Skiers in Yellowstone National Park have a winter wonderland of scenery to explore. Box On location (see text)