Charting the Unknown
On this day in history, September 22, 1688, French explorer Louis-Armand de Lom d’Arce, Baron de Lahontan, set out from Fort Michilimackinac on a daring journey into the uncharted west. His mission? To explore the waterways beyond the Great Lakes and, perhaps, uncover a route to the Pacific. Armed with a detachment of men and five seasoned Ottawa hunters, Lahontan embarked on a voyage that would be remembered for centuries. Partly for its adventurous spirit, partly for its enduring mysteries.
From Michilimackinac, his route took him across Lake Michigan, into Green Bay (then called Baie des Puants). Then up the Fox River, and across a portage to the Wisconsin River. From there, he descended to the mighty Mississippi. It was along this river that Lahontan claimed to have discovered the “Rivière Longue” (Long River), a waterway flowing west into unknown lands. Some scholars believe he had reached the Missouri River. There are others that think the Long River existed only in his imagination. Some say it was perhaps a strategic blending of fact and fiction.
Documenting more than the Land
Lahontan’s travels brought him into contact with numerous Indigenous nations, including the Hurons at Fort St. Joseph and other groups who had never before encountered Europeans. His detailed journals documented not only the landscapes and waterways but also Indigenous cultures, wildlife, and trade networks. These writings later became part of his Nouveaux voyages de M. le baron de Lahontan dans l’Amérique septentrionale, first published in 1703.
By the time he returned to Fort Michilimackinac in March 1689—240 days after departure—Lahontan had mapped large swaths of the western Great Lakes region, recorded invaluable cultural exchanges, and sparked debates among geographers that continue to this day. Whether the Long River was real or imagined, Lahontan’s accounts shaped how Europeans viewed the North American interior, influencing Enlightenment thinkers like Voltaire and Montesquieu.
In the centuries since, his writings have been scrutinized, celebrated, and sometimes doubted, but one thing remains clear: on this September day in 1688, Lahontan launched one of the most intriguing expeditions of New France—a journey where history and legend still intertwine.
