The notion that both expeditions were failures is true only in the sense that they couldn't find an easy water route across the continent. They couldn't find it because it wasn't there, and the discovery of what's there—and what isn't—is the definition of exploring success, not failure. That's why their negative findings were themselves valuable additions to the buildup of geographic knowledge about the West. The incremental nature of that buildup can be traced in the succession of maps produced as each page of discovery was turned. Vancouver's naval survey map of the Pacific Northwest was published in 1798, allowing Mackenzie to incorporate that coastline in his 1801 map of his route through the Rockies. These cumulative Vancouver-Mackenzie features, in turn, were used by American cartographer Nicholas King in his summary 1803 map given to Lewis and Clark at the outset of their trip. Clark's 1814 map relied on these previous benchmarks, while adding enormously to everyone's grasp of how the wide ranges of the Rockies are situated in the continent's interior.
Mackenzie's word pictures were as important as his map pictures. The Scot began his 1801 book with a disclaimer about his descriptive powers: "I am not a candidate for literary fame." After that, some readers might have been surprised by the author's detailed attention to the landscape and its animals and plants. After seeing tracks of "large bears," Mackenzie reported: "The Indians entertain great apprehension of this kind of bear, which is called the grisly bear, and they never ventured to attack it but in a party of at least three or four." In the murderous Peace River Canyon, he took time to name 12 kinds of local trees; "the shrubs are the gooseberry, the currant and several kinds of briars."17
As geopolitical propaganda Mackenzie's book failed to entice the British government toward a Northwest Pacific empire. Yet its dramatic portrait of the West—"the rude and wild magnificence of the scenery around"—made it a bestseller among ordinary readers in Europe. Similarly, Lewis and Clark returned to St. Louis in 1806 with first-hand news worth taking to the bank: the West is alive with beaver. Never mind the political dreams of globe-twirling statesmen in Washington, fur business entrepreneurs scrambled west the very next year to cash in.
Spanish explorers to the south had long before started weaving a skein of trails through the North American interior, to which Mackenzie and Lewis and Clark added their northerly contributions. If the feelers sometimes seemed to lead nowhere, the cumulative new layers of geographic insight told later travelers exactly how to go somewhere.
17. Sheppe, First Man West, p. 281. Mackenzie described grizzly bears on pp. 85, 89; the botanical descriptions at Peace River Canyon are on p. 101.