where three Hidatsa villages had stood when Lewis and Clark wintered in the area. I was retracing the explorers’ route, trying to connect their experience with my own over a gap of nearly two centuries, and had asked if I could spend a night in the earth lodge, which with a dusting of snow looked something like a sod igloo. Gerard seemed bemused by my request, but he agreed to accompany me, and, even provided our supplies.

First he smudged the interior in all four directions with the smoke from a bundle of sweet grass. “For the spirits,” he explained. Then, in an iron pot, he boiled potatoes, onions, red peppers, and buffalo tripe, the spongy membranes of a buffalo stomach—a rubbery meal that we ate with our hands. I told him tales about my trip upriver from St. Louis, about all the changes I had seen compared with what the captains had described in their journals. He shared stories of his ancestors and sang some Hidatsa chants. Outside, the northern lights began to dance while the temperature kept sinking. It was time to go to bed.

Gerard had brought along five large buffalo robes and advised me to place one of them, fur up, on the dirt floor as my mattress. The other four, he said, would provide more warmth stacked on top of me, fur down.

“But what about you?” I asked, thinking that he was taking Indian hospitality to a foolish extreme. In the back of my mind, I recalled Clark’s journal entry about two Indians who had stayed out all night on the frozen prairie and survived—proof, he wrote, that the “customs & the habits of those people has ancered [them] to bare more Cold than I thought it possible for man to indure.” The smudge ceremony, the meal of buffalo, the stories around the campfire, and now this, I thought. History was repeating itself.

“Are you sure you’ll be O.K.?” I insisted.

Gerard smiled at me. “I’ll be all right,” he answered, and he unrolled a fancy down-filled sleeping bag next to my buffalo robes. “This one’s guaranteed to twenty below.”

I have been out and back across the entire Lewis and Clark Trail three complete times since that evening in the earth lodge with Gerard. And more often than I can count, I have visited individual sites along their route. Yet every time my path has crossed theirs, I have wondered what the two captains would think if somehow they could be transported back to life in the modern world and sent out as, say, a Corps of Rediscovery. What would they recognize? What would confound them? What would they regret? What would they appreciate?

Certainly a frigid night on the northern plains would be painfully familiar to them. These were two Virginia-born gentlemen, accustomed to the mildest of winters; I doubt that they could ever forget their experience at Fort Mandan, where they were exposed

to one of the harshest weather extremes this continent has to offer.

I, too, have stood on the banks of the Missouri and been awestruck by its raw power as huge chunks of ice floated relentlessly downstream, only to be even more awed the next morning on finding the mighty river frozen solid, conquered by the cold. It’s something you remember. (In my case the memory is aided by a minor case of frostbite in my nasal passages, which still acts up whenever the mercury drops below zero.) In the column titled “Unchanged,” place a big checkmark for the ferocity of winters on the upper Missouri.

Nor would the captains find anything new in a meal of buffalo or in a Mandan’s willingness to share it with a stranger. But Lewis, I imagine, would be fascinated by Gerard’s sleeping bag—so light yet so warm, just the kind of scientifically advanced equipment he had scoured Philadelphia to find when outfitting his expedition. Whether the captain would appreciate the irony that in this case it was an Indian showing off the latest in technology to a white man—and poking a little fun in the bargain—depends on your own assessment of Lewis’s psyche. Personally I doubt it. In my mind’s eye I see him bristling silently as he tucks himself in between the buffalo robes. Clark’s the one who might have enjoyed the joke, even if it was on him. But he would also have been the one more troubled by a story Gerard told as the embers turned crimson.

In 1836, while an aging Clark was still Indian agent for the territory, the government sent two doctors up the Missouri with instructions to vaccinate all the tribes along the river against smallpox. They inoculated most of the tribes, but winter turned them back before they reached the Mandans, Ankaras, and Hidatsas. For some reason, the Secretary of War did not dispatch them to finish the job the next spring (and even misled Congress into believing the project was completed). That summer catastrophe struck.

When a fur-trading boat filled with supplies paid its annual visit, it also unwittingly brought the smallpox virus, which quickly spread among the unprotected Indians. Gerard has read all the eyewitness accounts as well as listened to the oral histories passed down through the tribes’ generations. Smallpox, he says, causes a “very, very ugly death”—sores that ooze and burst, swelling, aching, vomiting, delirium. In the villages people began dying at a rate of eight to ten a day. Corpses piled up; the stench of rotting bodies could be smelled for miles.

Fearing their protective spirits had abandoned them, some Mandans sought escape through suicide. After debating the bravest way to die, one warrior cut his own throat

while another forced an arrow into his own lungs. Some drowned themselves in the Missouri.

Among those struck by the sickness was Four Bears, a Mandan chief of some note. As a warrior he had killed five chiefs of other nations in hand-to-hand combat, wrested a knife from a Cheyenne warrior and used it to kill its owner, taken many prisoners, and survived an enemy arrow and six gunshot wounds. Like the rest of his people, he had always felt nothing but friendship for the white man. When the fever first hit him, he put on his ceremonial garments, mounted his horse, and rode through his village, singing his sacred songs. Then, as he, too, began to succumb to the disease, he gave a final speech to his people. A fur trader transcribed it, and it’s preserved in a book of tribal history that Gerard loaned me:

“Ever since I can remember, I have loved the Whites. . . . To the best of my Knowledge, I have never Wronged a White Man, on the Contrary, I have always Protected them from the insults of Others, Which they cannot deny. The 4 Bears never saw a White Man hungry, but what he gave them to eat, Drink and a Buffaloe skin to sleep on, in time of Need. . . . And how they have repaid it! With ingratitude! I have Never Called a White Man a Dog, but to day I do Pronounce them to be a set of Black harted Dogs, they have deceived Me, them that I always considered as Brothers, has turned Out to be My Worst enemies.

“I have been in Many Battles, and often Wounded, but the Wounds of My enemies I exhalt in, but to day I am Wounded, and by Whom, by those same White Dogs that I have always Considered, and treated as Brothers.

“I do not fear Death my friends. You Know it, but to die with my face rotten, that even the Wolves will shrink with horror at seeing Me, and say to themselves, ‘That is the Four Bears, the Friend of the Whites.’”

Along with Four Bears, 90 percent of the tribe perished in the epidemic. The prosperous nation, whose villages had constituted the biggest city on the plains during Lewis and Clark’s time, was reduced to barely a hundred individuals, huddled together with remnants of the Ankaras and Hidatsas.

Word of the devastation would have reached Clark in St. Louis shortly before he died. He was experienced in the loss of friends, but it must have greatly saddened him, “the Red-Headed Chief,” to ponder the fate of the people who had so warmly welcomed the expedition thirty years earlier. Showing up in Gerard’s earth lodge nearly two centuries later would undoubtedly have flooded him with even stronger emotions. Outside, the three villages once teemed with life and noise, while the smoke of cook

fires curled from the tops of hundreds of earth lodges, and neighbors and explorers alike shared food, music, and laughter to ward off winter’s chill. Now there are only large, circular depressions in the ground marking where each lodge stood, like so many supplicating palms outstretched on the barren plain.

My guess is that Clark would have had the same trouble sleeping that I did that night, hearing echoes of Four Bears’s words whenever the night wind hissed or a cottonwood groaned as it shook in the gale. And I imagine that he, too, would have hoped that Gerard had adequately appeased the spirits of friendship with the smudge of his sweet grass.

“We proceeded on” is the most recurrent phrase in the journals of the Lewis and Clark Expedition. Charles Floyd wrote it several times in the brief diary he kept before he died far from home—the first U.S. soldier to die west of the Mississippi but certainly not the last. His comrades Patrick Gass, Joseph Whitehouse, and John Ordway used it all the time as well. So did the captains.

With three matter-of-fact words they could describe the act of getting up each morning, facing an unknown horizon whose only certainty was another day of hard work, and pushing forward with, if not confidence, then at least dogged determination to move just a little farther toward that horizon before the sun went down.

“We proceeded on.” It became, in effect, the Corps of Discovery’s motto, a mantra that kept them going in the face of every obstacle. When I travel in their footsteps, I usually adopt it as my own. It reminds me that they didn’t have the luxury to look backward, to pause and contemplate the past. And it helps me conjure up their spirits to join me on my modern journey.

The captains in particular were Jeffersonian men, imbued with the Enlightenment notion of steady progress. “We proceeded on” could summarize their view of how the universe works. It would also influence their reaction to many of the starkest changes to be found along their route across the continent.

Lewis, who devoted so much time to scientific descriptions, would no doubt be enthusiastic about the agricultural transformation of the Louisiana Territory. The Missouri, he wrote his mother from Fort Mandan, “waters one of the fairest portions of the globe, nor do I believe that there is in the universe a similar extent of country equally fertile.” He would probably nod his head, as if to say, “I told you so,” upon learning that the area is now the food basket for the nation and much of the world.

Clark, with his keen eye for terrain, had marked locations on his map as likely places for future forts and settlements. The mouth of the Kansas River, where the Missouri bends sharply toward the east, was such a spot. He would enjoy, I think, the vista from his old campsite.

Where once two rivers met in the wilderness now rises the skyline of Kansas City, the largest city along the Lewis and Clark route west of St. Louis. Later I would show him Omaha and Bismarck and Portland, other towns that grew up at strategic places he had identified. “We proceeded on,” he might say.

More changes. A series of dams, built to prevent flooding and to provide irrigation and hydroelectricity, has turned much of the Missouri into more lake than river. The “sublimely grand spectacle” of the Great Falls, which Lewis described so ecstatically, is now dominated by a concrete barrier; except in times of unusually high water, the falls themselves are dry rocks. The same goes for the Columbia. Celilo Falls, the Long and Short Narrows, the Cascades—places that Clark noted for the “horrid appearance of this agitated gut Swelling, boiling & whorling in every direction”—are now entombed under reservoirs.

What would the explorers think of the two mighty rivers now? To them, the raging cataracts were magnificent, but they were also impediments. I can imagine Lewis noting ruefully at the Great Falls that their majesty had once reduced him to wishing for better words to describe their beauty—and then walking excitedly into the powerhouse to see how the turbines work. On the Columbia (and its tributary the Snake), Clark would be wide-eyed at the sight of deep-draft vessels blithely carrying cargo toward the twin cities of Clarkston and Lewiston, now officially designated as seaports though they are four hundred miles inland from the Pacific.

It would not escape their notice that the same dams that tamed the Columbia for boat traffic, and that generate electricity used as far away as California, have also virtually eliminated the salmon. The amount of salmon, Clark wrote in 1805, was “incrediably to say.” Even attempting to estimate their numbers seemed preposterous. I think he would find it equally incredible today if he went with me into one of the deeper recesses of the Bonneville Dam, where a single employee easily counts each adult salmon that manages to swim past a window looking out on the dam’s fish ladder.

Lewis and Clark would have other questions about wildlife. They would remember beaching their canoes for hours as a buffalo herd forded the river; going for several months during which encountering a grizzly bear was an almost daily event; seeing enormous elk herds and packs of wolves; being kept awake at night by the slapping of beaver tails; witnessing a midday sky darkened by huge flocks of wild geese; filling their journals with description after description of animals they had never seen before, in numbers beyond imagination; passing through a landscape in which, as they wrote, “the game is getting so plenty

and tame in this country that some of the party clubbed them out of their way.”

As we retrace their steps, I can see the captains craning their necks at every turn, looking expectantly for an abundance of animals and then turning to me for answers to what happened. I would have to tell them that some of the species they recorded have vanished entirely, that others are struggling back from the brink of extinction. “Most of your animals can still be found,” I would assure them, “but in smaller numbers and more secluded locations. We probably won’t be seeing many on this trip.” Another side of the same coin upon which the nation emblazoned, “We proceeded on.”

Likewise, we would encounter fewer Indians. Lewis and Clark had been the first to tell them they had a new “great father.” In their speeches the captains promised that he “has offered you the hand of unalterable friendship, which will never be withdrawn from your nation.” Moving from reservation to reservation along the modern trail, they would hear instead tales of lands lost and promises broken. For the Lakotas, the Nez Perces, the Shoshones, the Blackfeet, and the tribes along the Columbia, the offered hand had turned into a fist. Even for those tribes that never experienced war with the United States—like the Salishes and Hidatsas and Mandans—the handshake of friendship proved a bad bargain.

“Follow these councils,” Lewis had concluded his first speech to Western Indians, “and you will have nothing to fear, because the great Spirit will smile upon your nation, and in future ages will make you to outnumber the trees of the forest.” Even by the standards of the Virginia gentry, Lewis was acutely sensitive about matters of honor; seeing how his word was so cavalierly disregarded would start him sputtering and then, perhaps, send him into dark despair. Out of both anger and shame, Clark’s face, I think, would turn as crimson as his hair.

To cheer them, I’d take the captains through the White Cliffs of the Missouri in north-central Montana, protected by Congress from damming and development. This is another place where Lewis grew rhapsodic, writing for pages about “scenes of visionary inchantment.” I’d invite him to do what friends and I have done on several occasions: read passages from his journal and then look up from our campsite or canoe to see precisely what he had struggled to describe. With luck we might even see a bighorn on the cliffs.

On our journey together the captains would learn that the Western sky is still as big as it was for the Corps of Discovery, the horizons still as simultaneously intimidating and exhilarating. Nothing has changed the broiling summer heat on the plains or the startling fury of a prairie hailstorm—not to mention the maddening persistence of mosquitoes up and down the Missouri. And the mountains? To Clark they were the “Shineing Mountains.” Lewis called them “tremedious . .

. covered with eternal snows.” Snow still covers their peaks in midsummer; from a distance they still shine. Farther west, winters on the Pacific coast are still sodden with rain.

It was on the coast that the Corps of Discovery got into the habit of carving their names into tree trunks. From the journal accounts, it seems, few trees near the sea escaped their knives. Reading between the lines, I get the impression they emblazoned the date and their names and initials with particular gusto, relief, and pride, as the most tangible evidence they could think of to prove they had actually crossed the continent. But mixed in with those emotions was also a tinge of fear—fear that they might not make it back to their homes, that they would never be heard from again, that they and their remarkable achievements would be lost to history. Marking a tree was both a boast and a plea to be remembered.

The tree markings have long since disappeared. But other things now bear their names. On our hurried return toward St. Louis, I would point out some of them: towns, counties, and national forests, rivers and mountain passes, high schools and colleges, campsites and cafés, the Lewis and Clark Search and Rescue Association, and the Lewis and Clark 24-Hour Wrecking Service. Where they ran out of whiskey, there is a Lewis and Clark Distillery. Where they switched from eating horses to eating dogs, there is the Lewis and Clark Animal Shelter.

We could follow federal highway signs marked “Lewis and Clark Trail” all the way from the Pacific to the east bank of the Mississippi, where they embarked on their journey. Near St. Louis I would drive them over the Lewis Bridge and then the Clark Bridge before I dropped them off, on the Illinois side, at the Lewis and Clark Motel. “We proceeded on,” I would tell them on behalf of their nation, “but you weren’t forgotten.”

There would be much for them to report on to Mr. Jefferson, some of it with great pride, some of it with great sorrow. Before we parted, I would add one more bit of information, telling the captains about what happened back in North Dakota on the morning after the cold night in the earth lodge with Gerard Baker.

Thanks to his sleeping bag, Gerard woke up warmer than I did. My feet felt like blocks of ice, and it took some time near the fire to restore them. Gerard teased me, saying that in honor of my experience he might give me an Indian name; what did I think of “Man Who Sleeps in Buffalo Robes” or “Smells Like Tripe”? Then he invited me back for the summer, promising that we could visit a traditional sweat lodge he had built. A friendship was forming that has now lasted for a decade and a half—despite the distances between our homes and the differences of

race and culture.

We have many things in common. Among them is a passion for history, not just out of intellectual curiosity but based on a more practical belief: that the journey to a better future must include discovering the past and learning from it. And while our approach is to explore history by being clear-eyed about its darker moments, we both try to pay attention and respect to the spirits of those who came before us.

Gerard’s desire to keep alive the traditions of his people had led him to the journals of Lewis and Clark, one of the best-written records about the Mandans and Hidatsas before the epidemic that nearly ended the tribes’ very existence. My search to understand my nation, by retracing its pursuit of the next horizon, had led me to the same source. Along the trail of the Corps of Discovery, our paths had crossed, and if I could meet their spirits, I would thank the two captains for bringing us together.

That morning was as cold as the morning before. The sun was shining, but the temperature was not going to reach zero, and the north wind still howled. We had planned on hiking to the site of Fort Mandan, a walk guaranteed to be both bone-chilling and fatiguing. For a moment we considered staying put, near the comfort of our fire. But like Lewis and Clark, we were moved by the spirit of discovery. We packed up our gear and stepped out to face the new day. And then we proceeded on.