From migration to ecology, new knowledge makes new cartographic demands

In May, as part of his campaign to annex Canada, President Donald Trump called the border with his neighbour an artificial line that had been drawn with a ruler “right across the top of the country”. He suggested that the map of North America would look more beautiful without it.

Historians pointed out that the border reflected a complex history and an everyday reality for millions, but they also admitted that Trump wasn’t entirely wrong. Much of the border does follow a straight line – the 49th parallel – and the Americans and Britons who drew it up knew almost nothing about local geography.