The map that was a claim

A sixteenth-century map shows a river running west where no river runs. The cartographer had never been there, and the river was not a mistake.

Maps of that period were commissioned, and what they asserted served whoever paid. A westward river implied a navigable route to a market, which supported a claim for a trading licence; a disputed coastline was drawn in whichever position favoured the sponsor; and empty interiors were filled with features because an empty space on a map invited someone else's claim. The cartographer's own letters show he knew the river was speculative. He drew it with the same line weight as the verified ones because a distinction in line weight would have invited a question.

Historians therefore read old maps as documents of intention rather than as records of terrain. The useful questions are who paid, what decision the map was meant to support, and which features would have mattered to that decision. A fortress drawn larger than it was tells you about a negotiation; a town omitted tells you whose interests the omission served.

This is not only a problem of the distant past. Modern maps make choices that are invisible because they are conventional: which places get labels at a given zoom, which disputed borders are shown as solid, whose spelling of a city appears. Each is a decision taken by an institution, and each is read by users as geography.

The habit that follows is small and useful. Before taking a feature from a map, ask what the map was for. A road atlas, a tourist plan and a planning document will disagree about the same street, and none of them is wrong.