The expedition of Sir Alexander Mackenzie in 1793, across the continent to the Pacific Ocean, which he reached in lat. 52 20’ 48”, again suggested the possibility of linking together the trade of both sides of the continent.  In lat. 52 30’ he had descended a river for some distance which flowed towards the south, and wag called by the natives Tacoutche Tesse, and which he erroneously supposed to be the Columbia.  It was afterwards ascertained that it emptied itself in lat. 49 degrees, whereas the mouth of the Columbia is about three degrees further south.

When Mackenzie some years subsequently published an account of his expeditions, he suggested the policy of opening an intercourse between the Atlantic and Pacific oceans, and forming regular establishments through the interior and at both extremes, as well as along the coasts and islands.  By this means, he observed, the entire command of the fur trade of North America might be obtained from lat. 48 north to the pole, excepting that portion held by the Russians, for as to the American adventurers who had hitherto enjoyed the traffic along the northwest coast, they would instantly disappear, he added, before a well regulated trade.

A scheme of this kind, however, was too vast and hazardous for individual enterprise; it could only be undertaken by a company under the sanction and protection of a government; and as there might be a clashing of claims between the Hudson’s Bay and Northwest Company, the one holding by right of charter, the other by right of possession, he proposed that the two comparties should coalesce in this great undertaking.  The long-cherished jealousies of these two companies, however, were too deep and strong to allow them to listen to such counsel.

In the meantime the attention of the American government was attracted to the subject, and the memorable expedition under Messrs. Lewis and Clarke fitted out.  These gentlemen, in 1804, accomplished the enterprise which had been projected by Carver and Whitworth in 1774.  They ascended the Missouri, passed through the stupendous gates of the Rocky Mountains, hitherto unknown to white men; discovered and explored the upper waters of the Columbia, and followed that river down to its mouth, where their countryman, Gray, had anchored about twelve years previously.  Here they passed the winter, and returned across the mountains in the following spring.  The reports published by them of their expedition demonstrated the practicability of establishing a line of communication across the continent, from the Atlantic to the Pacific Ocean.