For years, Jefferson had heard of and read accounts of the various ventures of other explorers in parts of the western frontier.
Explorers and Conquistadors
In the early to mid 16th century there were numerous Spanish explorers and conquistadors such as Álvar Núñez Cabeza de Vaca and Francisco Vásquez de Coronado who explored the Southwest of North America and crossed the continent (east to west) in its southern regions. In the North American Southeast there were explorers such as Hernando de Soto. Various countries sent exploring parties into the interior of the Americas. They also explored the west and east coasts north to California and Labrador and south to Chile and Tierra del Fuego.
Robert de La Salle
He explored the Great Lakes region of the United States and Canada, the Mississippi River, and the Gulf of Mexico. La Salle’s major legacy was establishing the network of forts from Fort Frontenac to outposts along the Great Lakes, Ohio, Illinois and Mississippi rivers that came to define French territorial, diplomatic and commercial policy for almost a century between his first expedition and the 1763 cession of New France to Great Britain. In addition to the forts, which also served as authorized agencies for the extensive fur trade, LaSalle’s visits to Illinois and other Indians cemented the French policy of alliance with Indians in the common causes of containing both Iroquois influence and Anglo-American settlement. He also gave the name Louisiana to the interior North American territory he claimed for France, which lives on in the name of a US state. His efforts to encompass modern-day Ontario and the eight American states that border the Great Lakes became a foundational effort in defining the Great Lakes region.
Pierre Antoine and Paul Mallet
Pierre Antoine and Paul Mallet, brothers and French Canadian voyageurs, were the first Europeans known to have crossed the Great Plains from east to west. They first journeyed to Santa Fe, New Mexico from Kaskaskia, Illinois in 1739. Pierre Antoine and Paul Mallet were born in Montreal, Canada and moved to Detroit in 1706 and Kaskaskia, Illinois in 1734. From Kaskaskia, in 1739, they attempted to travel to Santa Fe, New Mexico with six companions and nine horses loaded with trade goods. On July 5, probably near present day La Junta, Colorado they encountered a village of “Laitane” Indians (Comanche). Among the Comanche was an Arikara Indian slave whom they hired as a guide to lead them to Santa Fe. He led them, probably following a route approximating the later Santa Fe Trail to Picuris Pueblo, New Mexico where they first met Spaniards and were “pleasantly received.” They proceeded onward to Santa Fe where they proposed opening trade relations between New Mexico and the French. After a nine month wait in Santa Fe, the response from the government in Mexico City was negative and they were told they had to leave. However, they were given letters encouraging trade by New Mexican officials.
A French explorer and frontiersman who lived among the Comanche and Wichita Indians for many years. He later worked for the Spanish government as a peacemaker, guide, and interpreter. He blazed trails across the Great Plains to connect the Spanish and French settlements in Texas, New Mexico, Missouri, and Louisiana. He led three Spanish expeditions that attempted unsuccessfully to intercept and halt the Lewis and Clark Expedition.
Sir Alexander Mackenzie was a Scottish explorer. He is known for his overland crossing of what is now Canada to reach the Pacific Ocean in 1793. This was the first east to west crossing of North America north of Mexico and predated the Lewis and Clark expedition by 10 years. He reached the Pacific coast on 20 July 1793 at Bella Coola, British Columbia, on North Bentinck Arm, an inlet of the Pacific Ocean.
David Thompson was a British-Canadian fur trader, surveyor, and map-maker. Over his career he mapped over 3.9 million square kilometers of North America and for this has been described as the “greatest land geographer who ever lived.”
After the general meeting in 1806, Thompson travelled to Rocky Mountain House and prepared for an expedition to follow the Columbia River to the Pacific. In June 1807 Thompson crossed the Rocky Mountains and spent the summer surveying the Columbia basin and continuing to survey the area over the next few seasons. Thompson mapped and established trading posts in Northwestern Montana, Idaho, Washington, and Western Canada. Trading posts he founded included Kootenae House,Kullyspell House and Saleesh House; the latter two of which were the first trading posts west of the Rockies in Idaho and Montana, respectively. These posts established by Thompson extended North West Company fur trading territory into the Columbia Basin drainage area. The maps he made of the Columbia River basin east of the Cascade Mountains were of such high quality and detail that they continued to be regarded as authoritative well into the mid-20th century.