First state of Conrad Malte-Brun's map of North America, issued immediately prior to the the addition of Lewis & Clark's expedition information on this map, which would be added in 1812.
The 1812 edition of the map is one of the earliest printed maps to include the details of Lewis & Clark's expedition and the earliest recorded map to show a river running between San Francisco and Great Salt Lake (Teguayo), a myth which persisted for the next 20 years.
This edition of the map incorporates the reports of Peter Fidler for the Hudson's Bay Company, by including a series of possible river courses to the west, leading to (and prospectively through) the Rocky Mountains. This was the information which showed the prospect of a water route or portage through the Rocky Mountains and to the Pacific. It was this information, along with reports from local Indians encountered on the expedition, which Lewis & Clark relied in choosing their path to the Rocky Mountains.
On the west side of the Rocky Mountains, a section of river flowing past Mt. Rainier includes a speculative water course which flows to the Columbia River. This was the route taken by Lewis & Clark which led to their locating a navigable route by water to the Pacific Ocean.
The additions coming from Peter Fidler and the Hudson Bay Company were the result of Fidler's extensive contacts with the indigenous tribes on the eastern slope of the Rocky Mountains and contributed greatly to the geographical knowledge of the region prior to the return of Lewis & Clark.