The dam's visitor center features large underwater observation windows that put me within inches of the fish. With just a flick of their powerful tails, the salmon rocket through a flume of water as forceful as an open fire hydrant. Though the region's salmon population has dwindled during the past century (in no small part because they must run a gauntlet of habitat-altering dams), I've arrived in time to witness the largest spring chinook run since at least the 1930s: More than 600 salmon an hour are swimming through the dam.

I've lived in nearby Portland for nearly a decade and have driven the Columbia Gorge many times, but this is the first time I've ever seen salmon anywhere except on my dinner plate. What's different about this trip is that I've spent the past week traveling on the river, not just alongside it. Each Saturday from mid-February through the end of December, the Columbia Queen, a quadruple-decker riverboat offering all the comforts of a deluxe hotel, leaves Portland for a weeklong cruise from the Pacific Ocean to the Idaho border and back again—a journey of nearly 1,000 miles.

As a Pacific Northwesterner, I'm chagrined to admit that I wouldn't have believed it was possible to cruise from the ocean to the edge of spud country. But this trip has convinced me that there's no better way to explore the region than to follow its very jugular—the Columbia River and its leading tributary, the Snake. In size, the Columbia is in the same league as the Rhine and the Ganges. But while other big rivers typically roll through one major city after another, the Columbia skirts only one—Portland. For most of its length, it slices through rugged and diverse wilderness of unsurpassed natural beauty.

It also slices through history, both human and natural. Lewis and Clark followed the Snake and the Columbia during their epic trek to the Pacific, and Indian tribes have lived along these banks since well before the Egyptians built the pyramids. The 161-passenger Columbia Queen putters along at the relaxed pace of 10 miles an hour and is never far from land. During my week on the river I had a chance to go ashore and explore nearby sights, such as the spring chinook run, that hurried drivers often rush past.

Each day of our voyage, we had several hours to visit places such as Pendleton, Ore., home of the famed Pendleton Roundup; the Whitman Mission, where 13 people were massacred in 1847; and the Tamastslikt Cultural Institute, a state-of-the-art museum with a trove of artifacts and multimedia displays that document the history of the Cayuse, Umatilla, and Walla Walla tribes. And unlike Lewis and Clark, who subsisted largely on elk and dog meat during their arduous trek, we passengers had satellite TV-equipped staterooms, five-course dinners, and—my personal favorite—a late-night "treats table" loaded with cheese, fruit, and delicious desserts.

The fact is, motorists who think they know the Columbia from driving along the edge have actually missed as much as they've seen, since mountain ridges, tunnels, guardrails, and electrical wires block much of the panorama. To get the whole picture, you have to get on the river and observe things from a salmon's perspective.

My trip begins on Saturday afternoon, when the boat departs from Portland for an overnight cruise to the coastal town of Astoria, where the mighty Columbia spills into the Pacific Ocean. Infamous among sailors, the mouth of the Columbia has long been dubbed "the graveyard of the Pacific" because tricky currents, ferocious winds, and a shifting sandbar have gobbled up more than 2,000 ships during the past two centuries. Riverboats don't venture out far enough to add to that number, but the Columbia River Maritime Museum—just a few hundred feet from the boat dock—let me vicariously appreciate the danger with its vast assortment of artifacts gleaned from the wreckage. One of the odder items is a surprisingly well preserved officer's dress sword that sank with the U.S. Navy schooner Shark in 1846 and was found on a beach in 1977. The museum's collection also includes historic scrimshaw, navigational instruments, and lighthouse logs.

Afterward, I hop a tour bus for a short ride up to the Astoria Column, atop Coxcomb Hill overlooking the town and waterway. Built in the 1920s to commemorate the early explorers, this lighthouse-shaped structure is the closest thing to the starting line for anyone following the Columbia River upstream.

In keeping with a quirky local custom, I buy a glider for 70 cents at the Friends of the Astoria Column gift shop, climb the 164-step spiral staircase to the observation deck, and pitch the glider over the edge. When launched into the wind, a glider can often sail like a hawk for 15 minutes or more before touching down. Afterward, glider pilots are welcome to retrieve their craft—if they can find it—and keep it as a fun souvenir.

Since I'll be following the same rivers that Lewis and Clark paddled nearly two centuries ago, I'm not about to leave the coast without making a pilgrimage to nearby Fort Clatsop. This is where the expedition members, dubbed the Corps of Discovery, resided during the winter of 1805-06, after crossing the continent. The National Park Service maintains a life-size replica of the explorers' log fort on the site of their original encampment. The stockade-like compound with its damp, spartan bunkhouses gives new meaning to the term "American primitive." Its trading-post-meets-fortress design sums up the self-serving relationship the expedition had with the local Clatsop and Chinook tribes: During the day, the explorers opened the gates to swap goods (not to mention venereal diseases) with the Indians; at sunset, they ushered the Indians out and locked the gates behind them.

With two hours of daylight left, I reboard the boat and head upriver, passing sandy beaches and forested riverbanks replete with deer. The next morning, we reach the 80-mile-long Columbia Gorge, a federally protected area shielded from extensive development. The gorge's western end boasts river-hugging mountains, thick evergreen forests, and a jewel box assortment of waterfalls that spew from the cliffs above. Noted for its scouring winds, the stretch of river near the town of Hood River is a world-class windsurfing destination. I've seen windsurfers from afar in the past, but from the railing of the riverboat, I am more than a distant observer. As a windsurfer skids by me like a water bug, we are close enough to exchange greetings.

Just east of Hood River, as the Columbia passes through the heart of the Cascade Range, the climate and terrain undergo one of the most abrupt transformations found anywhere in the world. Within the span of a few miles, the average annual rainfall drops by two thirds, and the drippy, Paul Bunyanesque rainforest gives way to the arid, treeless mountains of Frederic Remington. Studded with office building-sized chunks of black basalt, the rounded, largely desolate mountains look as if they're sprouting Easter Island statues.

This terrain owes its otherworldly appearance to a succession of Ice Age floods that tore through the region, beginning 20,000 years ago. In one such flood, a lake that covered much of present-day Montana burst its glacial dam, releasing a 2,000-foot-high wall of water that sheared away mountainsides and carried boulders as big as houses for hundreds of miles.

Rather than stop to appreciate the topography, most pioneers headed west to the fertile Willamette Valley as quickly as they could. Nonetheless, a few dreamers and oddballs actually came here because of the stark isolation. In the early part of the 20th century, for instance, a wealthy Seattle attorney named Sam Hill built a mansion on the river's northern bluff, near the town of Goldendale, Wash. Intending the mansion to stand for 1,000 years, Hill constructed it entirely out of reinforced concrete. He had hoped to found a utopian Quaker community on the surrounding property, but Hill's idea didn't fly with the Quakers—nor with his wife, who had no interest in settling down in the austere Washington countryside. His plans dashed, Hill converted the mansion into the Maryhill Art Museum. Stretching the definition of eclectic, the museum's collection includes Rodin sculptures, intricate Native American basketry, 1940s women's fashions, more than 250 ornate chess sets, and royal regalia once belonging to Hill's friend Queen Marie of Romania. On the same bluff, four miles east of the museum, Hill constructed a replica of England's neolithic Stonehenge as a monument to those killed during World War I. Hill's Stonehenge now stands more as a reminder of his monumental eccentricity. Near it is the crypt where he was laid to rest in 1931.

Not far from the town of Pasco, Wash., the Columbia Queen turns onto the Snake River and heads east toward Idaho.The rounded, scrub grass-covered mountains that surround the Snake are little changed since Lewis and Clark came through. A short distance upriver, we arrive at Ice Harbor Dam, one of eight dams we encounter during the course of the week. Unlike motorists, who see only the exterior of these engineering marvels, we actually cruise right through the dams' clammy innards, where locks raise and lower boats to the depth of the water on the other side.

Ice Harbor Dam is dark, dank, and redolent of a fishmonger's shop; traveling inside it is like visiting the river's basement. The passage begins when our riverboat chugs through a fortress-like gate at the front of the dam and halts inside the lock, a concrete canyon with walls as high as an eight-story building. After the gate closes behind us, a rising column of water gradually lifts us to the top of the lock before another gate on the opposite end opens, spitting us out onto the upstream portion of the river. We exit the lock exactly at sunset, in time to catch a flock of swifts performing their final aerobatics of the day before they veer into the mud nests they've built on the dam's twin towers.

I F   Y O U ' R E   G O I N G The 161-passenger Columbia Queen departs from its home port of Portland, Ore. An eight-night itinerary includes an overnight hotel stay in Portland and a seven-night cruise. For more information, visit www.deltaqueen.com. AAA Travel offers packages on the Columbia Queen with discounts of 10 to 50 percent for departures on Nov. 3 and Dec. 7. Contact the AAA travel center at (888) 937-5520. Several other companies offer year-round cruises on the Columbia River. Seattle-based Cruise West operates small cruise ships for 78 to 96 passengers. Call (800) 888-9378 or visit www.cruisewest.com. Portland-based American West Steamboat Company operates the Queen of the West, a sternwheel paddleboat that accommodates 163 passengers. Call (800) 434-1232 or check out www.columbiarivercruise.com. The Columbia Queen and Queen of the West have shorter (four- and five-night) itineraries available in March 2002.

The next morning, the Columbia Queen docks at the twin cities of Clarkston, Wash., and Lewiston, Idaho, which straddle the Snake River. Though almost 500 miles from the nearest salt water, Lewiston is deemed a seaport because of its navigable access to the Pacific. Beyond this point, the Snake becomes impassable for large boats. But the Columbia Queen has arranged for passengers to trek a bit farther by hopping aboard a jet boat for a half-day cruise due south on the Snake into Hells Canyon, which forms the boundary of Idaho to the east and Washington and Oregon to the west.

Imagine riding a dune buggy through a nature preserve at the bottom of the Grand Canyon and you'll have some idea of what it's like to jet through Hells Canyon. Here, river erosion and ancient seismic upheavals have sculpted a chasm up to a mile and a half deep. Gouged with staircase-shaped terraces, the mountains rise up on either side of the river like immense Aztec temples. Though mostly glass-smooth, the fast-running Snake occasionally tosses rapids in our path. At speeds topping 40 miles an hour, the jet boat shoots over the waves as if they were small speed bumps.

I wouldn't have guessed that, aside from rattlesnakes, either wildlife or humans could survive for long in this rocky gorge, which bakes like a kiln in the summertime. But around one bend, we come upon a flock of bighorn sheep grazing on a high precipice. On another stretch of river, we stop to observe Indian rock paintings depicting hunters and bighorn sheep. Though created nearly 7,000 years ago, the images—made from plant pigment, blood, and eggs—are as vivid as if they were painted last week.

We also arrive just in time to watch a recreational fisherman reel in a sturgeon, a bottom-feeding fish that can grow as big as a baby whale and live for more than a century. This particular fish, pale colored and nearly 10 feet long, can still anticipate its 100th birthday because the merciful angler releases it back into the river. Black bear, elk, mule deer, and bobcats call Hells Canyon home as well.

Later that afternoon, we return to Clarkston and board the riverboat for home. The return trip turns out to be at least as thrilling as the journey out, because we now see the landscape's desert-to-rain-forest split personality unfold as Lewis and Clark did when they canoed through this region.

West of Hood River, for example, we pass Beacon Rock, a basalt monolith that forms the plug of an ancient volcano and stands taller than the Seattle Space Needle. Though more than 140 miles from the coast, Beacon Rock is where the Corps of Discovery first observed the Pacific tide reverberating up the Columbia River. All around, lush conifers and fog-plumed mountains also signal that the edge of the continent can't be far away. Nearly 200 years after the fact, I feel the same excitement that Clark later expressed in his journal: "Ocian in view! O! the joy."