Mackenzie was born in the northern part of Scotland, in the picturesque and historic town of Inverness. The year of his birth is usually set down as 1755. In his youth he emigrated to Canada, and found employment as a clerk to one of the partners in the great Northwest Fur Company. Later on he went to Fort Chipewyan, on Lake Athabasca, and became one of the principal partners in the Northwest Company.

Mackenzie was endowed by nature with a powerful physique and a strong constitution, which enabled him to undergo the unusual hardships of his explorations in the wilderness. Beside these physical qualifications, he was inspired with the ambition necessary to the formation of great plans, and with an enterprising spirit which impelled him to carry them through to a successful termination. Great versatility of idea enabled him to oppose every novel and sudden danger with new plans, while a rugged perseverance, indomitable patience, and a boldness often bordering on recklessness, carried him through all manner of physical and material obstacles. In his dealings with the Indians and his own followers, he showed an unusual tact, a quality which more than any other contributed to his success. Nothing so quickly saps the strength and tries the courage of the explorer, be he ever so bold and persevering, as cowardice and unwillingness among his followers.

Nevertheless, Mackenzie was not a scientific explorer. Outside of the manners and customs of the various tribes with which he came in contact, only the most patent and striking phenomena of the great nature-world impressed him. No better idea of his views on this subject could be obtained than from a passage in the preface to his Voyages:

“I could not stop,” says Mackenzie, “to dig into the earth, over whose surface I was compelled to pass with rapid steps; nor could I turn aside to collect the plants which nature might have scattered on the way, when my thoughts were anxiously employed in making provision for the day that was passing over me. I had to encounter perils by land and perils by water; to watch the savage who was our guide, or to guard against those of his tribe who might meditate our destruction. I had, also, the passions and fears of others to control and subdue. To-day, I had to assuage the rising discontents, and on the morrow, to cheer the fainting spirits of the people who accompanied me. The toil of our navigation was incessant, and oftentimes extreme; and, in our progress overland, we had no protection from the severity of the elements, and possessed no accommodations or conveniences but such as could be contained in the burden on our shoulders, which aggravated the toils of our march, and added to the wearisomeness of our way.

“Though the events which compose my journals may have little in themselves to strike the imagination of those who love to be astonished, or to gratify the curiosity of such as are enamoured of romantic adventures; nevertheless, when it is considered that I explored those waters which had never before borne any other vessel than the canoe of the savage; and traversed those deserts where an European had never before presented himself to the eye of its swarthy natives; when to these considerations are added the important objects which were pursued, with the dangers that were encountered, and the difficulties that were surmounted to attain them, this work will, I flatter myself, be found to excite an interest and conciliate regard in the minds of those who peruse it.”

Thus Mackenzie writes in the preface to his journal. Nevertheless, there is no evidence throughout his works that he was learned or even interested in the sciences of botany or geology. The scientific mind becomes so much absorbed in the search for information, when surrounded by the infinite variety of nature’s productions, especially in regions hitherto unknown, that mere inconvenience, physical suffering, or imminent peril is incapable of withdrawing the attention from the chosen objects of pursuit. Whoever reads Humboldt’s narrative of travels in the equinoctial regions of South America, especially that part which pertains to his voyage on the Orinoco, will appreciate the truth of this. The stifling, humid heat of a fever-laden atmosphere, the ever present danger of sudden death from venomous serpents, ferocious alligators, or the stealthy jaguar, the very air itself darkened by innumerable swarms of mosquitoes and stinging insects, with changing varieties appearing at every hour of the day and night, were unable to force this great naturalist to resign his work.

Unfortunately, the explorer and the naturalist are not often combined in one person, notwithstanding that the fact of being one, implies a tendency toward becoming the other.

Mackenzie mentions one or two attempts previous to 1792 to cross the Rocky Mountains. No record of these expeditions is available, a circumstance that implies their termination in failure or disaster.

Up to this time the Rocky Mountains, with their awful array of saw-edged peaks covered with a dazzling white mantle of perpetual snow, had stood as the western limit of overland exploration, beyond which no European had ever passed. The Pacific Coast had already been explored by Captain Cook in 1778, and a few years later so accurately charted by Vancouver, that his work is still standard among navigators. The eastern border of the Rockies was vaguely located, but between these narrow strips there remained a vast region, four hundred miles wide, extending to the Arctic Ocean, about which little or nothing was known.

As in the case of other unexplored regions, there were vague and conflicting rumors among the Indians concerning the dangers of these upland fastnesses, accounts of hostile tribes, men partly human, partly animal in form and nature, and colossal beasts, endowed with fabulous strength and agility, from which escape was next to impossible. These Indian tales, though in great part the product of imagination or superstition, unfortunately did but partial justice to the reality, for although the reported dangers and terrors were mythical, there were real and material obstacles in the form of mountain ranges bewildering in their endless extent and complexity, between which were valleys blocked by fallen timber, and torrential streams rendered unnavigable by roaring rapids or gloomy canyons of awful depth. In fact, this region was one of the most difficult to penetrate and explore that the world could offer at that time.