Francis Drake's 1579 approach to the Northwest Coast had shown other mariners the difficulties of sailing the northeastern Pacific, and for nearly two centuries few ships had reached the Northwest Coast via the southern capes. In the mid‐ eighteenth century Russia approached the coast from Siberia and Kamchatka. At the same time Spain pressed north and west from Mexico into Alta California. Yet not until the British and the Americans in their wake conquered the watery wastes did the Northwest Coast between California and Alaska become profitable for European enterprise. Cook's third voyage placed Nootka Sound on world maps for the first time, and although his charts of the North Pacific gave mariners a rough idea of the ocean's littoral, they contained yawning blanks suggesting unknown islands and reefs, harbours, and hazards. Subsequent trading voyages by Meares, Duncan, Barkley, and others provided further details, and as a result of Vancouver's survey the main features of the coastline had been duly determined and charted.
Drake, Cook, and Vancouver all had been entrusted by their government with the same objective, to find a northwest passage linking the Atlantic with the Pacific. This waterway eluded each of them. In the case of Cook and Vancouver, inshore coastal exploration was needed to seek the passage, from which the British gained a comprehensive understanding of the intricate coastline. They compiled charts and views published by the government, navigational aids which were made available without restriction to mariners of other nationalities. Freedom of navigation on the high seas formed a tenet of Britain's maritime predominance, and the charts completed after Cook's and Vancouver's voyages enabled ships of any flag to approach the Northwest Coast. As a result of these two probes the chart showed not a vague shoreline stretching north and west from California to Alaska, but several large islands flanking the coast, including Vancouver and the Queen Charlottes, an entry into an inner passage from Cape Flattery via the Strait of Juan de Fuca, and an extensive arm of sea, Puget Sound, that would become in time a focal point of Pacific Northwest development. The chart also showed a maze of islands and channels separating Vancouver Island from the continental shore, numerous inlets penetrating eastward into the coastal mountains, and northward, beyond Cape Caution on the mainland towards the Gulf of Alaska islands, countless passages, and inlets.
Cook and, to a greater degree, Vancouver had shown how complex the coastline was between 49° and 60°N. It was a unique blend of offshore islands, straits,