Louis Armand de Lom d’Arce, baron de Lahontan (1666-1715?), was the son of a prominent civil engineer in the court of Louis XIV. In the 1680s Lahontan went to Canada with the Bourbon Regiment, where he served as Lord Lieutenant of the French colony at Placentia in Newfoundland. He commanded Fort St. Joseph in 1687 before deciding to return to the East coast the next year. Baron de Lahontan claimed to have traveled to the northern portions of the Mississippi River and to the villages of the Osage Indians on the Missouri River, but it was his journey to the Long River on his trip back that captivated the attention of adventurers who dreamed of finding a passage to the Pacific.
According to Lahontan, during a four-month journey in the winter of 1688-89 his party of three hundred men explored the Long River or, as it is labeled on his map, the "Rivière Morte" or "Rivière Longue." The expedition traveled up the Long River about 800 miles from the Mississippi. At this point Indians told him that he was about 450 miles from a great salt lake that was near some high mountains. Lahontan insisted that the Indians had shown him a map drawn on a deer skin which depicted a large river running to the western sea and he suggests this passage to the Pacific Ocean on his own map.
The account of Lahontan’s journey on the Long River, together with his travels throughout New France from 1683 to 1694, was entitled Nouveaux Voyages de Mr. le baron de Lahontan, dans l’Am‚rique Septentrionale. This book which included his original map of the Long River was published in The Hague in 1703 in two- and three- volume editions and in London in a two-volume English edition. In 1704 in Amsterdam Lahontan published separately an account of his conversation with an Indian, entitled Dialogues de Monsieur le baron de Lahontan et d’un Sauvage, dans l’Amerique. Lahontan’s works were widely published and very popular in Europe. The Long River appeared on other maps as late as 1785.
The University of Virginia Library Special Collections has copies of these French- and English-language editions. Thomas Jefferson owned the second English edition of 1735. Jefferson thought Lahontan’s work was important, despite the fact it was widely discredited by the second half of the eighteenth century. He recommended it for inclusion in a national library in 1783 and in 1785 included it among a list of books on American travel which he deemed "a useful species of reading for an American youth."