Red lines on maps: The impact of cartographical errors on the border between the United States and British North America, 1782-1842

In 1782 it was agreed that the frontier between the United States and British North America should run from the east to the Lake of the Woods, wrongly perceived (on the basis of Mitchell's 1755 map) as the westernmost of the Great Lakes, and then due west to the Mississippi. Other cartographical errors and misapprehensions also played a role in the fixing of the border. Thus in 1804 President Jefferson seized on the 49th parallel as the line supposedly agreed on after the 1713 Treaty of Utrecht for the border between the British Hudson's Bay territories and French (now American) Louisiana, and it was eventually adopted. The discovery of what was thought to be a conspicuous line of continuous highland south of the St. Lawrence, and the renewed attention paid in the mid-eighteenth century to the borders specified in King James VI's 1621 grant of Nova Scotia, helped frame the parameters of a dispute over what is now the Maine-New Brunswick border-one that periodically disturbed Anglo-American relations between 1783 and 1842. The negotiation of the Webster-Ashburton treaty that ended the dispute in 1842 provides another example of the selective use of maps in diplomacy.