GLACIER NATIONAL PARK, Montana — On sunny days, Lake McDonald shimmers like blue silk, enticing visitors to plunge into its richly colored water. But that would be a mistake. Hypothermia would quickly set in because the lake is fed by the same forces that formed it: glaciers.

So instead, I explored its waters the way so many other tourists have since Montana's Glacier National Park was created 100 years ago. I boarded a creaking wooden tour boat.

The double-decker DeSmet, with its varnished wood benches and thick coats of turquoise and white paint, eased from the dock with a low-grade rumble one bright morning this summer. From the open-air upper deck, I watched beyond the stern as mountains, still draped in snow, rippled in the water's reflection.

"We saw a bear and a bald eagle yesterday. Keep an eye out," our guide told us.

The DeSmet has been carrying tourists past such scenes since it was built in 1930. Before roads cut through the thick forest, the boat and others that preceded it ferried tourists from a point near West Glacier rail station, where many of them arrived, to Lake McDonald Lodge.

The boat ride was not my only brush with history. The evening before, I'd arrived by train — following the same remarkable route laid down by St. Paul's Great Northern Railway more than 100 years earlier.

I boarded Amtrak's Empire Builder at 10:30 one night in mid-June for the 21-hour trip to Glacier, fell into the bed of my sleeper car and awoke the next morning somewhere in the middle of North Dakota. Outside the window, ponds with ducks and cattails, bluffs with cattle and wildflowers, and the occasional small-scale oil well dotted the rolling landscape.

Passengers swayed down the aisle, keeping rhythm with the train's rocking, as they made their way to the dining car for breakfast. Others slept on their broad, reclined seats, legs sprawled across footrests and heads pressed into pillows decorated with SpongeBob or embroidered flowers.

Throughout the day, the train made brief stops at small towns with near-empty main streets. At one, a few passengers who know the timing of the line well scampered across the tracks to a bar advertising music and beer with rusting signs; it was time for their happy hour — more like 15 minutes.

"The scenery, plus no driving," said Roger Krob of Superior, Wis., explaining why he and his wife, Cora, take the train whenever they can.

I met the couple during our own true happy hour, a wine and cheese tasting for sleeping car passengers in the Empire Builder's dining car. As we sipped Oregon wines out of plastic cups and ate chunks of Wisconsin cheese on crackers — products from states on either end of the Empire Builder line — I learned that the Krobs were on their way to Sacramento, Calif., to attend a Laurel and Hardy convention. Roger, who resembles Stan Laurel, is the vice-sheik of Busy Bodies, essentially a group that celebrates the early Hollywood comedy team. Laurel and Hardy, it turns out, appeal to the Krobs because they represent a simpler time, when life was less complicated — a lot like the railroad.

That night at dinner, sitting beside a lifelong Montana farmer, I got my first jolting look at the Rockies — towering peaks that abruptly soar into view after endless miles of prairie. By dessert, the train was rolling past the southern border of Glacier National Park and its mountains of wilderness, lush gorges and whitewater rapids on the Middle Fork of the Flathead River.

It wasn't the majesty of the landscape that spurred St. Paul railroad baron James J. Hill and his son Louis to fight for its designation as a national park. Rather, it was its potential to generate money.

The route of their Great Northern Railway to the Pacific Ocean was laid down by 1893. With the help of Blackfeet Indians, the railway's engineer had found Marias Pass, the lowest point through the Continental Divide, at 5,216 feet. The Hills understood that a national park would bring riders to that relatively new route.

When Glacier joined the park system in 1910, the railroad company was ready. It built clapboard lodges adorned with window boxes and created ads designed to lure people to what they called "America's Switzerland." Its Belton Chalet was welcoming visitors just two months after the park opened — and it still is, even if rooms are spartan by today's standards. For my first day in the park, I headed to a grander accommodation, Lake McDonald Lodge, which opened in 1914.

The scenery on the Going to the Sun, the only only road that cuts through the park, was stunning: turn-outs led to rocky beaches or views of glacier-scoured mountains.

At Lake McDonald, I got a slightly different vantage aboard the DeSmet.

From his small cockpit, Capt. Fiske Firebaugh used a speaker system to tell his 18 passengers that something called glacial flour — minuscule particles of rock generated by glacial erosion — gives the lake its unique color. He told us that 14 other boats lie at the lake's bottom: "With all the wood around, it was easier to sink a boat and build a new one than to haul an old one out for repairs."

The boat glided past young evergreens taking hold amid the bare trunks of trees that had burned during the devastating fires of 2003. Firebaugh told us about the natural recovery of the forest, a happy tale of nature. But then he shared some sobering statistics: There are only 25 glaciers in this national park named after the frozen wonders of nature. Last year, the count stood at 27; in 1985, it was 150.

He added no commentary to the facts. But in answer to a curious visitor, Firebaugh explained, "I've learned not to say anything about global warming. It's not worth the fights."

Dr. Lyman B. Sperry, an early supporter of the park, once wrote, "Finding that a single day in this remarkable place could give but a taste of its delights, some of our party determined to visit again as soon as practicable."

I decided the same. I hadn't scaled any peaks, and I had yet to see a glacier because the highest parts of the Going to the Sun Road were still closed by snow in mid-June. But I knew my visit would have to be soon, while seeing one of the namesake glaciers is still possible.

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IF YOU GO:

THE BASICS: Glacier National Park became the 10th national park on May 11, 1910. It preserves more than 1 million acres of land carved by glaciers and includes 25 remnant glaciers in Montana's Rocky Mountains. Going to the Sun Road, the only road across the park, offers scenic views as it climbs over the Continental Divide. Snow makes it unpassable for much of the year.