A landmark map in the charting of the American West.

Arrowsmith first published his map in 1795 and by constantly issuing updated versions, as new information became available, he ensured that the map retained its reputation as the best general map for the American West. It was the 1802 edition that was used by Lewis & Clark to plan their own expedition of 1805-06; and the map’s 1814 edition is justlty famed as the first large scale map to incorporate their discoveries. It has been noted that the map is a great deal more accurate than the one published to accompany the first edition of Lewis & Clark’s travels. This is due to Arrowsmith drawing on numerous sources most notably from new information from the British explorer David Thompson – whose information helped greatly with the delineation of the Columbia river – and that of the Hudson Bay Company. The map also extends some way south to include the Gulf of Mexico; the information of which was taken from the works of Zebulon Pike and Humboldt. The revisions would continue with the present 1819 edition of the map drawing on the latest American maps including those of Darby and Melish.