Many European maps of North America in the eighteenth century depict a large, western inland sea, hundreds of miles in diameter, with a small inlet to the Pacific and even some interior islands. The origins of this myth can be traced to several different sources and are tied to the search for a Northwest Passage. Like many cartographic myths, the Sea of the West persisted for decades, even in the face of strong evidence pointing to its non-existence.
One of the first European navigators to supposedly explore this area was Martin Aguilar. A Spanish captain, he sailed with Sebastian Vizcaino on a reconnaissance expedition up the California coast in 1602-3. Aguilar, commanding the Tres Reyes, was blown off course, to the north. When the seas calmed, Aguilar reported that he had found the mouth of a large river. Eighteenth-century geographers later conjectured that the river was the entrance to the Sea of the West.
Other maps placed the entrance to the Sea of the West via the Juan de Fuca Strait. Juan de la Fuca is the Castilianized name of Greek navigator Ioánnis Fokás (Phokás). Little archival evidence survives of Fuca’s career, but a chance meeting with an English financier, Michael Lok, in Venice in 1596 gave birth to rumors of Fuca’s voyages in the Pacific. Fuca reported that he had been sent north from New Spain twice in 1592 in search of the Strait of Anian. The Spanish Crown failed to reward Fuca’s discovery of an opening in the coast at roughly 47° N latitude and Fuca left the Spanish service embittered. His story lived on in Lok’s letters and eventually was published in Samuel Purchas’ travel collection of 1625. On many eighteenth-century maps, Fuca’s Strait is linked with a River or Sea of the West. In 1787, the present-day Juan de Fuca Strait was named by the wife of naval explorer Charles William Barkley, making permanent a label that had previously just been hopeful guesswork.
The Sea of the West was speculated to exist by Guillaume De L’Isle, France foremost theoretical geographer, around the turn of the eighteenth century. It first appeared in print on maps published by Johann Baptiste Nolin ca. 1700, but it quickly disappeared thereafter.
The re-introduction of the sea in the mid-eighteenth century was the result of De L’Isle’s son-in-law, Philippe Buache’s review of his father-in-law’s papers. Although De L’Isle never published a map showing the sea, he had postulated that it could exist, and that it might connect to a Northwest Passage through New France, not through English territory farther north. Nolin had plagiarized the idea from Guillaume, as the latter testified when suing the former for plagiarism. He said, the Sea of the West “was one of my discoveries. But since it is not always appropriate to publish what one knows or what one thinks one knows, I have not had this sea engraved on the works that I made public, not wanting foreigners to profit from this discovery” (as quoted in Pedley, The Commerce of Cartography, 109).
The sea was a major part of Buache and Joseph-Nicholas Delisle’s maps of the North Pacific, published in the 1750s. While controversial, the features of those maps were quickly copied by other mapmakers, including the Sea of the West. The inland body of water lingered on maps until the later-eighteenth century.