“A Map Exhibiting all the New Discoveries in the Interior Parts of North America.” 1795, with additions to 1811.

Aaron Arrowsmith (1750-1823) began his career as a surveyor in England. He made several maps that appeared in John Cary’s popular Traveller’s Companion, an atlas of turnpike roads in England and Wales. In 1790 Arrowsmith started his own map- publishing firm. His maps and atlases soon earned him an international reputation for accuracy and fine engraving.

Arrowsmith produced his first map of North America in 1795 after the Hudson’s Bay Company had given him access to the many journals and surveys of western Canada contained in its archives in London. Arrowsmith’s 1795 map (not shown) incorporates details from the surveys of Peter Fidler in the Northwest through 1792, from Samuel Hearne’s explorations west of the Hudson Bay, from Alexander Mackenzie’s journey to the Arctic Ocean in 1789, and from George Vancouver’s chart of the Northwest coast and the “River Oregan” (lower Columbia River). The 1795 map shows a vestige of the “Great River of the West” and the Missouri River appears as a river fragment unconnected to either the “Stony Mountains” or the Mississippi River. Arrowsmith also includes a note stating that the “Stony Mountains” are “3520 Feet High above the Level of their Base and according to the Indian account is five Ridges in some parts.”

The 1802 revision of the map of North America, on display, delineates the complete length of the Missouri River as well as Mackenzie’s journey to the Pacific in 1793. The depiction of the Missouri headwaters, which Arrowsmith studied from Peter Fidler’s drawing of a map by the Blackfoot Indian Ac Ko Mo Ki, shows several streams joining into two branches of the Missouri which flow almost due east. The southern branch of the Missouri appears to be the main branch of the river and connects to the Knife River; the northern branch is a good representation of the actual course of the Missouri.

Although the revised map still shows a single ridge of mountains in the west, a note near the southern sources of the Missouri states: “Hereabout the Mountains divide into several low Ridges.” This note, which was based on the reports of Fidler, Mackenzie, and Thompson, was more encouraging to Jefferson and Lewis than the note about the Stony Mountains on the 1795 map, which, unfortunately, turned out to be more accurate. Arrowsmith’s map situates the Great Lake River on the western slopes of the mountain range and connects this river to the Columbia River with a dotted line. Since another note claims that this river can be descended to the sea in eight days, the Arrowsmith map supported the erroneous belief in a convenient route to the Pacific Ocean.

Both the 1795 and 1802 versions of Arrowsmith’s map served as resources that Nicholas King consulted as he prepared his map for the Lewis and Clark Expedition. Lewis and Clark, in fact, carried the 1802 Arrowsmith map along on the expedition. Thomas Jefferson owned the 1802 map as well as an 1802 edition of Arrowsmith’s map of the United States. Arrowsmith’s 1802 map of North America was the most comprehensive map of the West available to Jefferson and Lewis and it was probably the most important map used in the planning of the expedition.

The map on display is the lower half of “A Map Exhibiting all the New Discoveries” from an edition labeled “1795, with additions to 1811.” The lower half of the map is identical to the 1802 edition. Numerous revisions of this map were published until 1850.

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