Except for the few Russian traders who obtained sea-otter pelts in western Alaska and sold them in Mongolia, the northwestern corner of North America remained outside the range of European knowledge until the last quarter of the 18th century. In 1770 trade in land furs had not reached the Mackenzie drainage basin and barely touched the Rocky Mountains (Exploration from Hudson Bay, 17th, 18th Centuries, Fur Trade in the Interior, 1760-1825: Concise Plate 60), while the Spanish (who claimed the entire West Coast of the New World) had just begun to establish outposts in southern California. On world maps of the day northwestern North America was blank.
This was soon changed. In the mid 1770s the Spaniards Pérez and Quadra sailed north along the West Coast in search of Russian interlopers. Finding none, they quickly left. In 1778 a British expedition under Cook spent a month at Nootka on Vancouver Island, then sailed northward to search for the passage that the admiralty thought might lie about 60°N. After Cook the broad outline of the Northwest Coast was known. In the early 1790s British and Spanish surveys, the most extensive by Vancouver, filled in many details.
The fur trade expanded rapidly into the Athabaska country (Fur Trade in the Interior, 1760-1825: Concise Plate 60) after Peter Pond, an American-born trader based in Montreal, was shown the Methye portage between the Saskatchewan and Mackenzie drainages in 1778. In 1789 Alexander Mackenzie, another Montréal trader, followed the Mackenzie River to its mouth; in 1793 he crossed the continental divide, reached the Fraser River, then left it to follow an Indian trail to the Pacific. At the same time the Hudson's Bay Company encouraged exploration and mapping, sending a trained surveyor, Philip Tumor, to Rupert's Land in 1778, and making HBC maps and journals available to the cartographer Aaron Arrowsmith in London after 1790. The Arrowsmith map of 1795 is the first to show northwestern North America in approximately correct proportion. After Simon Fraser descended the Fraser River in 1808 and David Thompson the Columbia in 1811, the geographical framework of western Canada was known.