His first two years of service brought nothing but disappointment and disillusion to David Thompson. Vaguely sensible of his capacities, he was conscious of nothing except that as yet he had been given no scope to realize them. But in the summer of 1786 a new and important chapter opened in his life. Fitted out with a trunk, a handkerchief, shoes, shirts, a gun, powder, and a tin cup, he was included in a party of forty-six "Englishmen" who left for the interior under the leadership of Robert Longmore to establish trading posts on the Saskatchewan river to the west of those already occupied by the Company.

For over one hundred years from the time when the merry monarch had vested in them a monopoly of trading rights in the vast territory whose waters drain into Hudson Bay, the "adventurers of England trading into Hudson Bay" had maintained their factories on the coast, and allowed the Indians from the interior to make their way to them for trade. Great rivers flowed from all directions to the Bay; but the courses of these rivers were still unknown to the map makers of the British Admiralty in 1784, the year in which David Thompson landed at Churchill. For Hudson Bay is encircled from Labrador on the north-east to the Arctic on the north-west by a giant horse shoe of Archaean rock, most of it clothed with the dense northern forest; and so long as the red men were willing to make the tedious journey up and down the rivers, the slumbering giant on the Bay was content to accept the annual tribute of furs which they flung at his feet. Each September, when the ships from London arrived, the factories were crammed with pelts that meant a fortune on the markets of the Continent; and the traders eagerly awaited a fresh supply of guns, axes, and kettles for the Indian, and awls and beads for his squaw, as well as the fire-water which made him the anxious though reluctant slave of the great white chiefs on the Bay.

But the monopoly of trade to which the Company laid claim had not been accepted without challenge. On the eastern face of North America, the St. Lawrence river points like a finger to the heart of the continent, and from the head of Lake Superior it is possible, by a comparatively easy portage, to cross the height of land and descend through Rainy lake, the Lake of the Woods, and the Winnipeg river to Lake Winnipeg. Lake Winnipeg forms a vast collecting basin for the waters of the interior, before they finally discharge through the Nelson river into Hudson Bay. Thus it affords communication south and west by way of the Red and Assiniboine rivers through the prairie country of southern Manitoba, the Dakotas, and Minnesota; while, from the north west corner of the lake, the Saskatchewan carries the traveller to its sources in the Rockies. While therefore the English had waited for the Indians to bring their furs down to them on the Bay, the French from Quebec had pushed their way along these waters to the heart of the hunting grounds, and the advance of these gallant adventurers was marked by a string of forts that extended from Dulhut's post at the head of Lake Superior to Fort La Jonquière near the site of Calgary.

The fall of Quebec in 1759 had brought with it the destruction of the organized French fur trade, and the traders were scattered through the wilds. But new groups of adventurers, mainly of Scotch descent, swarmed westward from their headquarters at Montreal, and penetrated into the wilderness further than the French had ever gone. By the year 1772, the Montreal traders had crossed from the Saskatchewan to the still more northerly Churchill river, and cut the line of communication ordinarily used by the Indians of Lake Athabaska in their long journey to Hudson Bay. The consolidation of the rival interests into one great firm—the North West Company—was accomplished in 1784 at the very time of Thompson's arrival in the West. This achievement brought vastly increased strength to the Montreal traders by mitigating the evils of their fierce competition. Thus the Hudson's Bay Company was threatened with the loss of its fur supply at the same moment as the French war interrupted its convoys, and La Pérouse swept the Bay, destroying the posts at Churchill, York, and Albany.

Energetic measures were necessary if the lost trade was to be recovered. As early as 1774, Samuel Hearne had taken the momentous step of founding the first inland post of the Hudson's Bay Company at Cumberland House. Situated on the Saskatchewan a few miles west of Lake Winnipeg, Cumberland House stood, as it were, in the centre of a vast web of waterways. "A canoe could start from this house, and with no portage of more than a day's length could be launched on the Arctic ocean, Hudson Bay, the Gulf of St. Lawrence or the Gulf of Mexico; and without much greater interruption could be floated on to the Pacific ocean." Despite the disasters of the French war, and the dreadful epidemic of smallpox which in 1781 had swept across the West, decimating and demoralizing the natives, the advance of the Company was continued by the establishment of further posts along the Saskatchewan river. Thompson was thus drawn into the forefront of the battle for furs, when he was included in Longmore's party in the summer of '86.

On the 21st of July, the brigade of canoes left York factory for the upper country. Longmore, the chief, was well qualified for the task of leading the expedition. For many years he had served as lieutenant to Tomison, the "chief inland" of the dépôt at Cumberland House. Here he had acquired the difficult knack of dealing with the Indians, besides earning their love and respect. Thompson's immediate superior was Mitchell Oman, an old and experienced trader of the Company, to whom he had been assigned as clerk. Oman could neither read nor write, but he nevertheless impressed the lad by the unusual quality of his curious and inquisitive mind. During the tedious paddle into the interior, he drew from the pages of a retentive memory endless tales of the Company's early activities inland. "In those days," he declared, "our situation was by no means pleasant. The Indians were very numerous, and although by far the greater part behaved well, and were kindly to us, yet among such a number there will always be found bad men. To protect ourselves from them, we had to get a respectable chief to stay with us and assist us in trading, and prevent as much as possible the demands of these men." His valuable reminiscences were not lost upon the boy.

As the boatmen slowly worked their way up the river, Thompson's eyes gazed for the first time on the country he was afterwards to know so well. Their course lay up the Hayes river, and thence, by way of Lake Winnipeg, to the Saskatchewan. Progress at first was rapid, even against the stream, for they were still in the low and marshy country that fringes the south-west corner of the Bay. Presently, however, they encountered the first of the many rapids which mark the descent of the river to the sea. At each of these, with monotonous reiteration, the packs were all heaved ashore and shouldered along the rugged path of the portage to the higher level of the river. At the same time, the face of the landscape suddenly altered. The marshy alluvial gave way to naked granite, and they entered the belt of dark and gloomy northern forest. As they passed through the heart of the rocky country, the character of the river was also changed. From point to point the stream was held back by ledges of granite which broke its progress, giving rise to an irregular chain of wide and deep lakes. Through these lakes they threaded their way until, reaching the end of the granite country, they saw before them the broad expanse of Lake Winnipeg, the "bad water" of the Indians. Sixty miles along its northern coast brought them to the point where the Saskatchewan, after a swift and unbroken course of over one thousand miles through the plains, plunges in a long series of cascades into the lake. Having portaged past these, and wended their way through the alluvial flats of Cedar lake, they came at last to Cumberland House, and the first stage of their journey was accomplished.

Their objective was a point on the Saskatchewan about fifty miles above the present site of Battleford. As they continued their journey westward from Cumberland House, the forest gradually gave way to open country, and they found themselves in the vast expanse of the plains, dotted here and there with clumps of trees—the country of the bison, the antelope, and the red deer. Passing the forks of the river, they came to the site which the keen eye of Longmore had selected. There, on the northern bank of the stream, they cleared the ground and ran up a series of log huts, surrounded by a wooden stockade—the future Manchester House. Except for a solitary post which the North-Westers had for three years maintained about forty miles further up stream, Thompson had now reached the limit of country at that time familiar to civilized men. To the west stretched the unknown wilderness, which it was his destiny, in considerable measure, to explore.

The object of the new post was to secure the trade of the natives of the plains; and during the following winter David was busy learning the complicated ritual of Indian barter. In the course of a year he had so far mastered his duties that he was selected to lead a party of six men across country to the south branch of the Saskatchewan, in order to open friendly relations with the Piegan and Blackfeet Indians whose camps lay along the banks of that stream. Each man had a horse, and among them they carried a small assortment of goods. The duties of the young diplomat were to find the camps of the Piegans and winter among them, in order to induce them to hunt for furs and to make pemmican or dried buffalo meat for the traders. He was to persuade as many as possible to travel to the post for trade. With those who were unwilling to do so, he was to bargain for furs.

The party set forth in October, under their seventeen-year-old leader. The trail they followed led through a fine rolling country, everywhere clothed with short grass, and dotted with islands of poplar and birch. For twenty-three days they rode without seeing any animals other than a chance bull-bison which they shot for food. To the south of the Bow river they found an Indian camp pitched in a spot where the tender grass afforded rich pasture for the buffalo; but the plains, which were ordinarily black with moving herds, were at this time strangely deserted. After several moves, they finally struck a large encampment of Piegans near the present site of Calgary. Sending some of his men back to Manchester House, Thompson settled down in this camp to spend the winter.

The Piegan, Blood, and Blackfeet Indians were three allied tribes of Algonquin stock who had emerged from the northern forest and taken possession of the plains, driving their enemies, the Kootenay, Salish, and Snake Indians, before them to the mountains. Since the white men had come to trade on the river, they had advanced from the Eagle hills in western Saskatchewan to the very foot of the Rockies. This rapid conclusion of an age-long struggle for the mastery of the grazing country had been due to the fire-arms which they had procured from the traders.

The manners and customs of the confederate tribes were in keeping with their war-like disposition and constant danger. Unlike the scattered forest Indians, they lived in large camps, and without yielding their traditional liberty to the control of a single authority, they had nevertheless evolved a rudimentary form of social organization. Hunters of the bison, they were in constant need of horses. Horse-stealing was thus among them an honourable pursuit, and their raids extended far to the south and west. During the winter of Thompson's stay among them, a raid on the Snakes took a part of two hundred and fifty warriors a distance of one thousand, five hundred miles to the south-west, as was testified by the thirty well-bred animals that were brought back to camp, and the Spanish saddles and bridles that lay thrown about among the tents.

Of the three allied tribes, the Piegans occupied the most exposed position, and consequently led the most precarious and watchful life. From boyhood they were trained in arms, and their martial bearing and enterprising character produced a strong impression upon Thompson. They had an hereditary civil chief or "orator", as he was called, who presided at all councils except those of war. Arrayed in his splendid mantle of otter skin, he paced the camp each day three hours after sunset, reciting in a loud voice the news which his couriers had gathered, announcing in particular where the herds of bison were feeding and what direction they were taking. The war chief, on the other hand, was a self-made man, whose power and influence had developed from his conduct in war. Kootanae Appee, as he was called, was a magnificent giant, six feet six inches in height, and was the father of twenty-two warriors, no less tall and sinewy than himself. In after years, when Thompson was battling his way south along the Columbia river, the bond of friendship which he now forged with this old chief stood him in good stead.

The chief in whose tent Thompson passed the winter bore the name of Saukamappee (Young Man). Saukamappee was broad of shoulder and strong of limb. Old age had not bowed his grey head, nor had a troubled life obliterated the mild and playful expression of his countenance. During the long winter evenings, he entertained his guest with reminiscences that went back for fifty years. From him, Thompson learned of the Indian methods of fighting before the time of firearms, of the first importation of these deadly weapons from the distant factory at York, of the introduction of the horse among the Blackfeet, and of the dreadful effects of the small-pox epidemic in '81, of which Saukamappee himself had been a victim. While Thompson thus learned the history of the tribes among whom he was staying, he practised himself in the use of their language. His note books contain long lists of Indian words with their English equivalents, gathered from the Piegans and from other tribes whom he encountered.

The winter over, Thompson returned to the post, from which he was sent to Cumberland House in the summer of 1789. Here he began to keep a careful meteorological journal, noting two or three times daily the temperature, the strength and direction of the wind, and the general character of the climate. He also began a series of astronomical observations, as the result of which he was able to determine the exact latitude and longitude of Cumberland House. This post was thus the first of a series of widely scattered points fixed by him on the map of British North America. It was then, too, that he acquired the large brass sextant which was to be his constant companion for years to come.

Having made this start, Thompson attempted in the following summer to make a survey of the canoe route from Cumberland House to York factory, by way of the Saskatchewan and the Hayes rivers. In the autumn, he returned to Cumberland House. While there, he had the good fortune to meet Philip Turnor, the man without whose guidance and help Thompson could hardly have realized his future career.

For several years, the Colonial Office had been urging the Hudson's Bay Company to proceed with the survey of the vast territory over which it exercised sway; and to satisfy the pressing demand of the government, the Company had engaged Philip Turnor as astronomer and surveyor. Possessed of a sound theoretical training, Turnor had been employed in England as one of the compilers of the Nautical Almanac; and since 1776 he had added to his qualifications a wide practical experience drawn from numerous surveys throughout the region of the Bay. Here was a man who could solve Thompson's doubts and difficulties, and correct the deficiencies of his education for the work which he had in view. An eager pupil, Thompson sat at the feet of Turnor during the winter of 1790; and when, in the following spring, he returned to York factory, it was as a man with his mind made up. If a man knows clearly what he wants and has the intelligence and perseverance to pursue his aims, no obstacle, not even such as these which confronted Thompson, can keep him from attaining his goal.

Thereafter Thompson and his beloved instruments were inseparable companions in journeys that carried him for thousands of miles through the wildest parts of the unknown west. By day and night, he was an object of wonder to his French-Canadian and Indian followers, as, armed with his sextant, telescope, compass, and other instruments, he took observations on the sun, moon, and stars. While he sought to determine the position of rivers, lakes, and mountains, to be recorded on the map which was to be his life's work, his activities suggested to their superstitious minds the idea that he was in communication with powers not of this world, and earned him the title which he bore among them, Koo-Koo-Sint, "The man who looks at the stars."