The trees that form the boreal forest along the Yukon River mark the time elapsed since the last cataclysm. In the wake of fire or flood or axe, willows and alders are the first to root. Balsam poplar grow into the majority after two decades; white spruce after two centuries; black spruce emerge as sentinels of land that has gone the better part of a millennium without great disturbance. Seen from our boat on the river, the passing trees offer a history in the vertical, the measure of years visible in greens from silver-pale to inky dark.

We are on the Porcupine River, half a day’s travel still from its confluence with the Yukon River. Gwich’in land. Stanley Njootli and I have known each other since I moved to his village on the Porcupine as his dog-sledding apprentice more than twenty years ago. Now in his seventies, he’s become like a second father, and he remains spry and keen to spend weeks with our lives tethered to his flat-bottomed aluminum boat as we travel towards the Yukon’s Delta, where in the long meeting of the river with the Bering Sea the channel grows to half a mile wide. Stanley has friends in every village, and family in many of them. I know no one who can better read the tempers of water, or of people.

It is June, when the Arctic sun’s only concession to darkness is a brief 2 a.m. twilight. The solar glut makes the willow and poplar so dense with new leaf they can conceal a thousand-pound young bull moose and his shadow. Amid this vegetation, it’s several days before I discern the signs of people. A triangle where a cabin roof meets walls. The right angles of tent poles lashed to hold canvas. The stakes of a fish rack, ready to hold the split bodies of salmon over smoke. Tree growth carries a touch of the circular. Human geometry snags the eye. The exception is where beavers are at work. From mid-river, their felled poplars look like the beams of a cabin in early construction. It’s only when we pull near to the bank that we can tell who cut the line in the trees.

Between here and the sea, more than a thousand miles, no village on the Porcupine or Yukon can be reached by road. Or rather, the river is the road and has been as far back as there are stories. It is fitting, then, that we are heading downriver following a particular story, that of a place called Nulato.

‘There is only one way to settle ourselves in this country,’ wrote Ferdinand Petrovich Wrangel’ in 1832. ‘Namely, to settle on the Kvikpak River itself.’ Wrangel’, who managed the empire’s colonial venture in Alaska, the Russian-American Company, did not know that Kuigpak meant big river in Yup’ik, the language of the people of the Yukon Delta. Nor did he know how far inland the river ran, how many people lived along it, or what they called themselves in what languages. Yet, ‘No matter the difficulty of this undertaking, I will stop at nothing,’ Wrangel’ wrote of moving onto the river now known as the Yukon. He knew the upriver country was rich in beavers, and he was on the hunt for pelts.

I am on the hunt for the Russian Empire, or what traces might still exist of its colonial enterprise, which ended a mere thirty-five years after Wrangel’ wrote his letter. In the stories that define Alaska’s history, the Russian presence here is usually passed over for the gold rushes and oil wells, for earth-searing damage. What Russia took – the lives of animals – can regenerate. But the act of taking has a legacy even if the most visible scars have faded. No theft is free.

On the river, time is marked in other ways, and by other cataclysms. I first heard of the tensions between the Russian traders and Native peoples on the Yukon when I came north to work with Stanley’s dog team. By day, depending on the season, I trained huskies or fished or cut wood. By night, I listened to stories. This was long before I became a historian by trade – at eighteen I barely knew Russia had once been an empire – but I kept a sporadic journal. One entry, near-illegible from water stains, reads: ‘C.A. says the Gwich’in once went downriver to repel the Russians.’ My notes are not generous, but the line was an aside, told midstream in a story about conflicts in Gwich’in history that I was too shy to interrupt. But I remember the emotional peal, the sensation of dread and curiosity, because of the next word in my journal, now smudged: massacre.

And so, even before I even knew its name, I have wanted to see Nulato. I have gone looking for it in archives – in the records of the Russian-American Company, where Nulato is listed as a trading post with tallies of beaver furs, or in a file of old photographs at the University of Alaska Fairbanks. One photograph in that collection shows a wooden cross, inscribed: deriabin: killed by koyukok indians in the nulato massacre, feb 16 1851. But much of the history of the Yukon River lives with the river. We are traveling downstream looking for the signs of the past that are inseparable from place.

I hear the beaver first, a percussive sound breaking over the grumbling hum of our Honda outboard. Beavers, when aggrieved, slap the water broadside with their tails, a crack and splash before they dive. I signal to Stanley and he throttles back the engine. We wait to see where the whiskered head will rise.

The beaver surfaces fifty feet downstream, just the break of water over the muzzle showing, and the glint of the black eyes. Vigilant, but not warning us of trespass. Water is a beaver’s element: their paws webbed, their tail a paddle, their body kept dry by a dense, almost downy coat under sleek guard hairs. Few furs are warmer, or more resistant to damp. The beaver dives again. Stanley turns the boat back into the main channel. A bright afternoon, tender and warm. A few clouds pass delicate shadows over the far hills, black spruce and blueberry brambles.

We come to the first village, Fort Yukon, in the evening. Gravel roads, dusty with summer heat. Children shrieking with glee from bicycles. White spruce thick behind town. A history of past floods, some houses sitting empty and shifted askew by the power of high Yukon water, others bright with new paint. We have a lot of visiting to do – I have friends here, and Stanley says, not really joking, that half the town are his relatives.

My first stop is to see Richard Carroll. Brisk and with the build of a man who chops his own firewood, we met last time I was in Fort Yukon and have corresponded ever since. He is a historian of this part of Gwich’in country, and texts me periodically – always in all caps, often at 1 a.m. – to see if I might have a document he needs. I come bearing copies of census records: a trade, of a kind, as I have questions about the Russian Empire.

I find Richard pottering in part of an old cabin that is now his office, surrounded by sloping piles of church registers and books about the fur trade. While he heats water for tea, the conversation loops through the past distant and proximate – the forest fire twenty years ago that changed caribou migration, the height of the river (too high), the temperature this summer (too warm). With steam rising from mugs of Lipton, Richard turns to the serious history, a story about Shahnuuti’, the nineteenth-century Gwich’in leader from Fort Yukon so formidable he survived being bitten by a grizzly. I ask if Richard has ever heard about a Gwich’in altercation with the Russians. Richard considers. ‘Well, no,’ he says, speaking of the past in the present tense. ‘Not fighting, not us going down that way to fight, I don’t think.’ He pauses. ‘But we do hear things, even that far away. How many people downriver died of smallpox, I think it was. Some epidemic. We hear stories up this way of their men bothering women.’ He gives me a sharp look. ‘And I tell you, what I know about Nulato is, you kill two white people, that’s a massacre.’

In 1835, three years after Wrangel’ had promised to build settlements on the Yukon River, a Russian-American Company agent named Vasilii Donskoi opened an odinochka – a small trading post, no more than a log cabin – in the village of Iqugmiut, two hundred miles inland on the Yukon. In his first season, Donskoi sent 850 beaver skins back to Russia.

The pelts were bound for places that had slaughtered their local beavers. The Eurasian species, Castor fiber, had been extinct in Britain and was rare across much of Europe since the 1500s. In western Russia, hunters trapped fur species to scarcity and exported their pelts. By the middle of the sixteenth century, the Russian Empire answered this lack by sending trappers and Cossacks east into the Siberian taiga. Musket-armed soldiers coerced the Ket, Even, Selkup, Koryak, and Siberia’s other indigenous peoples to pay tribute in pelts; animal death became the price of stopping violence or restoring hostages. The land claimed by the tsars doubled by 1620, with fur revenues filling state coffers. French furriers began calling beaver Castor de Mosckvie for its association with Russia. Puritans wore felted beaver – produced using a Russian technique – across the Atlantic. Rembrandt drew himself in a beaver hat. Vermeer painted the lush sheen of light on beaver fur. Napoleon Bonaparte wore a beaver bicorn at Waterloo. Even the dried-stiff bundles of North American beaver, Castor canadensis, arriving from the British, Dutch and French colonies could not sate the demand.

A beaver gives birth only once a year, and four kits is a large litter. Already by 1683, Siberia’s military governors had reported that the ‘forest-dwelling natives have trapped all the available animals’. One response, in the face of such visible extermination, would be to restrain the pace of killing. Russia’s imperial leaders kept driving eastward. Wrangel’ knew the pattern: eradicate and move on. Even with good returns from the outpost in Iqugmiut, he ordered traders to continue up the Yukon. The river’s beavers were, by then, among the last in the world unharrowed by imperial commerce.

In Fort Yukon, we check the propeller for dents, repack tools, tents and coffee – ‘a disaster to run out’, Stanley says, more than once, so we have five pounds – along with blue plastic bins of pancake mix, Toll House cookies, and pilot bread, an indestructible round cracker best eaten with bone marrow or seal fat. The wind is calm, the sun is at its perennial summer slant, never far above the horizon. Ahead, the river eases into the slow, braided channels of the Yukon Flats, unrestrained by hills for nearly two hundred miles. It is a country with fewer people than moose.

As we travel, I look into sloughs for chewed branches, a paw-mark in mud – signs of beaver life, and also the life that their work shelters. The habit of selecting alder and birch for building dams and lodges shapes the forest, as does their method of coppicing willows. The ponds, which beavers form into moats against lynxes and wolves, are home to insects that feed bivalves, bivalves that feed fish, fish that feed eagles and bears. In ecological terms, their presence makes the land home to more life, in both kind and quantity. A beaver lodge marks a diffuse, vital abundance.

When we reach the next village, a day later, Stanley and I visit with Paul Williams Senior and his son, Paul Williams Junior. We spend a languid day cooking caribou meat in the yard and telling stories, or listening, in my case. The men are all fluent in Gwich’in and in speaking it their faces carry the joy of a thirst sated. I grow drowsy from food and the hot sun – ‘Too hot,’ Paul Junior says. ‘The sun is too strong these days.’ Stanley leans over. ‘He says it was Shahnuuti’,’ Stanley nods to Paul Senior, ‘who went downriver by canoe. With many men, cooperating with the Koyukon, because of how the Russians were acting.’ Stanley pauses. ‘There is a story that the first white man’s boats we saw were around that time, near here.’

There are many stories about Shahnuuti’ in Gwich’in country – Richard Carroll’s was one of them. Stanley has many. In the middle of the nineteenth century, he was the most formidable man in this part of the world, brilliant and terrible by turns. His grave is perhaps a hundred and fifty miles upriver from us, a known place – and a reminder that not so long ago, no tsar or foreign market set the terms of life here.

That evening, in my orange tent on the riverbank, I dig through my Helly Hansen rain gear and mosquito repellant for the waterproof bag that holds my computer and its scans of the Russian-American Company records, the correspondence of Wrangel’. I do not expect to find Shahnuuti’s name; the letters are sparse in such detail. But there is always a hope that the past will slot itself into a clear joint, this fact meeting another fact, the right angle of interpretation obvious. I fall asleep in a thicket of nineteenth-century Cyrillic handwriting, one word arcing into the next, a directive from long ago: ‘You are advised to go until you reach the place where the language changes and the forests begin.’