Fundamental map of the American West based on Spanish sources showing the sources of the Mississippi-Missouri.

This is the most famous of the maps published by Samuel Lewis and Aaron Arrowsmith in their “New and Elegant General Atlas” of 1804. The main source of for this map is the manuscript of the St. Louis surveyor, Antoine Soulard who drew a map of the upper Mississippi for Baron Carondelet, governor of Spanish Louisiana in 1795. Lewis also integrated further sources into his map such as the information on Samuel Carver’s map of North America published in 1778 as well as reports from the Missouri traders, Jean Baptiste Truteau and Jacques d’Eglise. The fundamental geographical feature of this map is the exaggeration of the western extent of the source rivers to the Mississippi-Missouri.

This exaggeration had a profound historical consequence. As this map was published in 1804, Meriwether Lewis (no relation to the map maker responsible for this map) and William Clark were preparing for their expedition into the American West to survey the Louisiana Purchase. It is known that Lewis was in possession of an English edition of Antoine Soulard’s map. Since the original wording of the Louisiana Purchase, finalized in 1803, defined its limits as “the drainage basin of the Mississippi River” Lewis and Clark no doubt expected to travel far further west than the actual modern limits of the drainage basin. This expectation ultimately led them to the Pacific northwest coast.

Despite these inaccuracies, this became the best and most important commercially available map of this vast region until Lewis and Clark’s own map was issued in 1814.

One of the great mysteries about this map is how Samuel Lewis obtained the information from Soulard’s map which was known in only manuscript examples; this is something that has never been explained. It has been suggested that Arrowsmith may have provided the information but this is now believed to be unlikely as there are geographical features on this map which Arrowsmith had already updated and corrected on his own maps. The most notable of these are the discoveries of George Vancouver on the Pacific Northwest coast, which are absent on this map but which Arrowsmith had already recorded in 1802.

Despite its small size and academic appearance, this is one of the key documents for available to the collector who has an interest in American westward expansion and the formation of the United States.

The example offered for sale here is the 1812 edition published in Boston by Thomas and Andrews. [USA10000]