This is a story of how one piece of flawed journalism snowballed a myth that appeared on over 200 historic maps. Before the late 18th century, the Pacific Northwest of North America was one of the last remaining geographical voids left on the planet. This was despite the centuries-long ambition to discover a Northwest Passage (NWP) – a maritime “Holy Grail” promising a shorter trade route between the Atlantic and Pacific Oceans.
Source: University of MichiganIt is into this atmosphere of high geopolitical stakes that one of the most successful pieces of historical ‘fake news’ was inserted. It all began with a letter, purported to have been written by a Spanish commander, Admiral Bartholomew de Fonte, in which he claimed to have successfully navigated the NWP in 1640.
Source: archive.orgThe first appearance of De Fonte’s ‘translated letter’ was in 1708 within an obscure, short-lived English periodical, the Monthly Miscellany, or Memoirs for the Curious. It was no surprise then that the story remained off cartographers’ radars.
The identity of the original perpetrator has been variously attributed to the magazine’s editor, James Petiver. Yet the presentation of the letter as a Spanish translation was particularly strategic. By claiming the discovery originated from a Spanish Admiral, the author imbued the text with foreign authority that could avoid immediate critique or libel.
De Fonte’s Alleged 1640 Voyage
To succeed as an authoritative document, the De Fonte letter provided precise details regarding the voyage’s commander, his fleet, the mission’s purpose, and key geographical landmarks.
The central persona was Admiral Bartholomew de Fonte, grandly described as the “Admiral of New Spain and Peru, and now Prince of Chili”. The voyage supposedly commenced on 3 April 1640, from the Callao of Lima, with four ships under De Fonte’s command: the St. Spiritus (the Admiral’s ship), the St. Lucia (Vice-Admiral Don Diego Pennelossa), the Rosaria, and the King Philip.
The ostensible mission added a layer of international political drama highly appealing to European readers. De Fonte’s voyage was explicitly ordered by the Viceroys of New Spain and Peru to intercept “industrious navigators from Boston” who were attempting the NWP.
Source: archive.orgDe Fonte described his journey north, discovering an entrance in 53°N latitude, the strategically important location of the “Rio de Los Reyes”. From this river, the route led through a “vast archipelago” and a complex system of interconnected inland waterways, culminating in a great inland sea.
The most critical and politically effective moment in the narrative was the supposed encounter deep within the continent. De Fonte claimed his crew met a westward-bound ship hailing from Boston, New England. Its commander, Captain Shapley, confirmed they had sailed successfully from the Atlantic side of the continent. This multi-party verification was the fictional proof required to convince contemporary analysts of the passage’s navigability.
Source: archive.orgPolitical resurrection of the fake news
Despite its meticulous detailing, the De Fonte letter lay forgotten for more than thirty years. Its resurrection in the mid-18th century was not an organic rediscovery, but rather a calculated political manoeuvre.
The 1740s saw renewed anxiety over the control of access to North America. Russian explorations in the North Pacific, led by figures like Bering and Chirikov, sparked Western European fears that a rival power might monopolise the NWP. This external pressure created an urgent need for proof that a passage existed and could be controlled by Britain or France.
Source: University of Washington
Source: University of WashingtonThe catalyst for the hoax’s transition into the mainstream was Arthur Dobbs, an Irish merchant and powerful advocate for the NWP. Dobbs harboured an intense political antagonism toward the powerful Hudson’s Bay Company (HBC), which he accused of maintaining a monopoly over the fur trade by suppressing evidence of viable passage routes near Hudson Bay. Dobbs championed expeditions, such as Captain Christopher Middleton’s, but ultimately sought decisive proof to discredit the HBC.
In 1744, Dobbs successfully weaponised the De Fonte narrative by including it in his influential book, An Account of the Countries Adjoining Hudson’s Bay. The letter’s implications were perfectly suited to his agenda, suggesting a route could be easily exploited by Britain.
The hoax achieved its peak legitimacy when prominent scientific and intellectual figures analysed it as a legitimate document. The renowned Benjamin Franklin took an enthusiastic interest in the account. In a detailed, thirteen-page analysis, Franklin summarised his view of the De Fonte letter as:
Source: Wikimedia
“…really a Translation from the Spanish, and not, as some have supposed, an English Fiction.“
This endorsement by respected, scientific-minded men shifted the burden of proof from the sceptical cartographer to the explorer. The British Parliament, responding to the pressure generated by Dobbs and others, offered £20,000 for the discovery of the NWP (equivalent to over £2 million today).
Source: GoogleMapping the fictional Sea of the West
The successful De Fonte letter provided the missing justification needed by cartographers to graphically represent a vast inland sea in the Pacific Northwest, known as the Mer de l’Ouest (Sea of the West). This feature became one of the most persistent and recognisable geographical myths of the 18th century, appearing on over 200 printed maps between 1700 and 1810.
The theoretical concept of a large internal body of water, the Baye ou Mer de L’Ouest, lies with Guillaume Delisle, the Royal Geographer to the King of France. He had depicted this speculative feature on his manuscript maps around 1700. However, Delisle, valuing rigorous “scientific integrity,” refused to publish a map containing such a massive, unverified feature, stating that it was “not always appropriate to publish what one knows or what one thinks one knows”.
This integrity was abandoned by others. Jean-Baptiste Nolin plagiarised Delisle’s manuscripts and published the first printed map featuring the Sea of the West around 1700, though this initial appearance did not gain widespread traction.
Source: BNFThe true cartographic rise of the myth occurred in the 1750s when Guillaume Delisle’s successors, his half-brother Joseph-Nicolas Delisle and his son-in-law Philippe Buache, resurrected and formalised the model. Together, they synthesised the De Fonte narrative with the claims of another apocryphal voyager, Juan de Fuca.
The resulting cartography, exemplified by Buache’s 1752 map, presented a complex, yet internally consistent, fictional hydrography. The system combined De Fuca’s alleged 1592 discovery of a strait at 47° N (which lent its name to the modern Strait of Juan de Fuca) with the vast internal geography described by De Fonte.
Source: New York Public LibraryThe Mer de l’Ouest itself was depicted as a huge body of water, extending hundreds of miles inland, often shown with interior islands. This sea then connected through long, elaborate waterways to “Lake De Fonte,” which abutted the known regions surrounding Hudson Bay.
Source: BNFThe French cartographers’ enthusiastic adoption of this model led to its widespread institutionalisation. The depiction of the Mer de l’Ouest became particularly common on French maps, cementing its status as a geopolitical tool supporting French territorial claims and exploration goals.
Fact-checking comes to the rescue
The belief in the De Fonte passage and the Mer de l’Ouest persisted for more than half a century, largely because proving its absence required massive, expensive, state-sponsored voyages. The cost of geographical ignorance, sustained by the hope of the NWP, was immense.
The geographical myth finally came to an end through the systematic work of British naval surveyors. The first major blow was struck during Captain James Cook’s third voyage (1778). Cook sailed from the Oregon coast, along the entire Pacific Northwest coastline, and through the Bering Strait. His lack of discovery of any vast inland sea or major, obvious opening, such as the Rio de Los Reyes or the entrance to a vast Mer de l’Ouest, fundamentally undermined the fiction.
Source: RMGCook’s explorations, though not systematic in every inlet, gave the first accurate form to the coastlines of modern British Columbia, Washington State, and Alaska, causing a rapid rearrangement of the old ideas about the region on subsequent maps.
Source: Stanford University
Source: BPLThe definitive proof, however, came from Cook’s former lieutenant, Captain George Vancouver. Between 1792 and 1794, Vancouver led a meticulous, systematic survey of the entire Northwest coastline, specifically entering the Strait of Juan de Fuca and exhaustively charting the inland waters, including Puget Sound.
Vancouver’s expedition confirmed that a passage connecting the Pacific to the continental interior in the manner described by De Fonte did not exist. His comprehensive surveys also definitively proved the non-existence of the vast Mer de l’Ouest.
The irony of the hoax lies in its ultimate effect: though the 1708 letter was a fabrication, its revival became a primary driver for the real-world, high-stakes explorations that ultimately brought accurate geographical knowledge to the North Pacific. The De Fonte letter is also a great example of how, sometimes, defeating persistent ‘fake news’ is achieved only through costly and systematic physical verification.
Further reading:
Dobbs, A., 1744. An account of the countries adjoining to Hudson’s Bay, in the north-west part of America.
Jefferys, T., 1768. The great probability of a North West Passage.
McGuirk, D.L., 2022. The Last Great Cartographic Myth: Mer de l’Ouest.