The idea of a great inland sea occupying a vast part of the American west and opening into the Pacific attained the height of its popularity in the middle part of the 18th century under the patronage of the influential French cartographers Guillaume de l’Isle and Phillipe Buache. Under Buache and De l’Isle’s influence the Sea of the West, Mer de L’Ouest, or Baye de l’Ouest reached its fullest expression and commonly appeared on maps from about 1740 to 1790.
The source of Sea of the West, however, precedes both Buache and De l’Isle by several hundred years. The idea of a Sea of the West is intimately related to the hope of either a Northwest Passage or a River passage from the Atlantic to the Pacific. Such a passage was actively sought after almost from the earliest days of American Exploration. The idea had at its core the commercial interests of British and French traders who, unlike the Spanish, had no easy access to the Pacific and the rich trade with Asia.In it most embryonic form, the Sea of the West can be associated with Verrazano’s sea. This great sea, pictured here in Munster’s classic 1540 map of the Americas, was identified by the Italian navigator Verrazano. Sailing along North Carolina’s Outer Banks in 1524, Verrazano saw the sound on the eastern side of the isthmus and postulated that it must be the Pacific.
. . . where was found an isthmus a mile in width and about 200 long, in which, from the ship, was seen the oriental sea between the west and north. Which is the one, without doubt, which goes about the extremity of India, China and Cathay. We navigated along the said isthmus with the continual hope of finding some strait or true promontory at which the land would end toward the north in order to be able to penetrate to those blessed shores of Cathay …
This concept was taken up by various cartographers back in Europe and, subsequently, a great indentation along the western coast of America starting just north of California was a common characteristic of many early maps of the continent. Even in the 1670s, when John Lederer made his famous explorations of Virginia and North Carolina, most colonial settlers believed that the western sea was only about 10 or 15 days inland from the coast.
Nonetheless, Verrazano’s Sea was largely discredited in the late 18th century when prominent cartographers like Ortelius, Mercator, Hondius, and Blaeu removed it from their maps. It was not until the 17th century that it began to reappear on maps though reformatted to a reduced size and moved farther west.The next serious first hand evidence of the Sea of the West appears in the account of Juan de Fuca’s voyage along the western coast of America published by Samuel Purchas in his 1625 book Purchas His Pilgrimes. The veracity of de Fuca’s account has been the subject of significant debate over the last 100 years or so. Most argue that de Fuca’s account was fabricated by the Englishman Michael Lok to promote his own ideas of a Northwest Passage. However, we find a grain of truth in the narrative. De Fuca was supposedly a Greek Captain active in the Americas in the late 1500s. Colonial records to indicate that such a figure did in fact exist and was an active pilot in New Spain from about 1585 to 1600. De Fuca’s account does ring somewhat of truth if we assume that he actually sailed into the strait now named after him:
…until he came to the Latitude of fortie seven degrees, and that there finding that the land trended North and north-east with a broad inlet of sea, between 47 and 48 degrees of Latitude; he entered thereinto, sayling therein more than twenty days, and found that Land trending sometime North-west and North-east, and North, and also East and South-eastward, and very much broader Sea than was at the said entrance, and that he passed by divers lands in that sayling…
Regardless of any actual veracity De Fuca’s account may or may not have, what is important for our purposes is the effect this report had on European cartographers who widely trusted it. In accounting for De Fuca’s 20 days of sailing, European cartographers, began mapping a large open inlet extending well into the continent – though perhaps not so far as the 16th century Verazanno’s Sea.The next incarnations of the Sea of the West – and perhaps it fullest realization – came through the work of the aforementioned Guillaume de l’Isle and his brother in law Philippe Buache. In the early 17th century it became increasingly important for French and English settlers along the northeastern coasts of North America to find a passage to the Pacific in order to compete with the Spanish for the lucrative East India trade. Both nations sent out several expeditions both by sea and by river. By this time, most agreed that an Arctic route was unfeasible and instead turned their attention to the lake and river systems of the continent. Some believed they would find a river system extending westward from the Hudson Bay along the passage mapped out by Juan de Fuca. Others postulated a more southerly route through the Lake of the Woods and Lake Winnepeg. Still others believed that a route could be found by following the Missouri River.
Such was the competition to get to the Pacific that, when De l’Isle and Buache “discovered” the Sea of the West, they chose to keep it a secret for the benefit of France and never published it in any of their works. It was left up to the competing map publisher Nolin to abscond with a copy of De l’Isle’s map and publish the first Buachian “Sea of the West” map. De l’Isle subsequently filed a law suit against Nolin for copyright infringement,
Il (Nolin) a represente une Mer a l’Occident de la Louisiane, qu’il appelle Mer de l’Ouest. Cette mer estoit une de mes decouvertes, mais comme il n’est pas toujours a propos de publier ce que l’on scait, ou que 1 ‘on croit sqavoir, je n’ai pas fait graver cette Mer sur les ouvrages quej’ai rendus publics, ne voulant pas que les Etrangers profitassent de cette decouverte quelle qu’elle pft estre, avant que l’on eut reconnu dans ce Royaume si l’on en pourroit tirer quelque avantage..
Even so, the damage was done and the Sea of the West began to appear on a number of influential maps of the period.
Of course, one wonders at De l’Isle and Buache’s sources. On this we have some certain evidence and a great deal of speculation. Reports from American Indians of a salt sea far to the west were hardly uncommon in the 18th century. De l’Isle would have had access to numerous missionary reports that were, at the time, streaming into Paris from the new world. At the very least, he would have had access to the narrative of Lahonton (who heard about the Great Salt Lake from his American Indian Guides), Juan de Fuca’s legend, the De Fonte letter, the influential though possibly fabricated tale of the American Indian traveler Moncacht-Ape, as well as the explorations of Pierre de La Verendrye.With so many sources and such a history, one might be tempted to ask why De l’Isle and Buache claim to have “discovered” the Sea of the West. The stems from the a cartographic approach embraced by Buache. Cartographers had the difficult job of piecing together legends, missionary reports, astronomical observations, and nautical references into a cohesive whole. It was their job to present the known world in a comprehensible manner. Even with reports from navigators and missionaries coming in from all over the world – much was unknown and much else was unreliable. In these instances cartographers resorted to a number of different strategies. Some filled the space with sketches, drawings, text or cartouches. Others simply left unknown areas blank. Some coped the speculations of other cartographers. By early 18th century, a new movement had evolved in France to address these problems. Though undefined at the time, today it is called “theoretical cartography”. Buache was the leading theoretical cartographer of his day. Theoretical cartography attempted to used known geographic patterns and scientific theories to fill in blank spaces when little else was known. The Mer de la Ouest is the perfect example Though a salt water inlet from the Pacific had long been speculated upon and hoped for, Buache and De l’Isle embraced the theory because it supported both the ambitions of the French crown in the New World and the theoretical geographic theory that Buache was developing.
The Sea of the West remained on map until the end of the 18th century. The late 18th century explorations of James Cook and George Vancouver finally defeated the theoretical cartographers.
Lucie Lagarde, “Le Passage du Nord-Ouest et la Mer de l’Ouest dans la Cartographie Française du 18e Siècle, Contribution à l’Etude de l’Oeuvre des Delisle et Buache, Imago Mundi, Vol. 41 (1989), pp. 19-43.
Hayes, Derek, Historical atlas of the Pacific Northwest, p. 18-27.
Petty, C. M., When France was King of Cartography, p. 113 – 164.
Kellog, L. P., The French Regime in Wisconsin and the Northwest.
Winsor, Justin, The Mississippi Basin: The Struggle in America Between England and France 1697 – 1763.