John Mitchell (1711-1768) was born in Virginia and educated at Edinburgh University in Scotland; he practiced as a physician back in Virginia before retiring to London in 1745. A botanist, Mitchell was soon adopted as an expert on exotic plants by the avid gardeners among Britain’s high society (Berkeley and Berkeley 1974). One of those gardeners was the earl of Halifax, president of the Board of Trade and Plantations, who also used his new colonial friend as an expert on the affairs of Virginia and of North America generally. By 1749, Halifax had recruited Mitchell to make a large and detailed map of the British and French colonies. At the time, the leading politicians in Britain were seeking a territorial compromise with the French in order to avoid further war. But Halifax used the final version of Mitchell’s map to persuade both his government colleagues and the British public, that such a compromise would be utterly disastrous. When published in London by Andrew Millar in March 1755, as A Map of the British and French Dominions in North America, Mitchell’s map quickly spawned a host of smaller, cheaper derivatives that widely publicized Halifax’s stringent interpretation of Britain’s colonial territories (Edney 2008)
The Mitchell map was used by negotiators in 1782 to define the boundaries of the fledging United States of America. The final boundaries were published in the Treaty of Paris, 1783. Yet the Treaty’s description of the U.S. boundary was ambiguous and the eastern portion of the US-Canadian boundary remained in dispute. Diplomats continually referred back to Mitchell’s map in order to resolve the treaty’s ambiguities, achieved in 1842 for the landward boundary and 1984 for the seaward boundary. The map’s legal and diplomatic use led Col. Lawrence Martin, when chief of the Library of Congress’s Geography and Map Division, to call Mitchell’s map “the most important map in American history” (Martin 1934).