Maps: Every Map Has a Story to Tell

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Every Map Has a Story to Tell

A compelling story could be told about almost any map in this exhibition. Here are a few.

Cultures Cross in Tenochtitlan
When Hernan Cortés entered the ancient city of Tenochtitlan he was stunned by what lay before him. The Aztec capital was not only enormous – bigger than Paris in its day – but politically organized and technologically advanced. A carefully planned city constructed in the middle of a mountain lake, it boasted broad avenues and causeways, busy canals, ornate temples and public buildings, wide bridges, aqueducts bringing water from distant mountains, bustling markets, botanical gardens…and armies of street cleaners and garbage collectors, something unheard of in Europe.

How could Cortés describe to Charles V, King of Spain, the city he had conquered? And how could he boast of his conquest and at the same time justify holding captive the ruler of a civilized nation? His second letter to the king is exuberant and detailed – but the map he sent with it tells even more.

Though the woodcut made from the map uses European techniques, including buildings shown in perspective, some scholars believe it is based on an indigenous Aztec map and embodies the culture’s idea of Tenochtitlan, grounded in the way the Aztecs viewed the cosmos. At the map’s center is the temple precinct, surrounded by a circular city set in the middle of a circular lake – ideal rather than actual spatial relationships. The temple precinct’s great expanse and dozens of buildings are reduced to its most significant and symbolic elements: two oversized pyramids with the sun rising between them, racks for human skulls, and a headless sacrificial victim or idol at the pyramids’ base. To the Aztecs, says one scholar, the ritual of human sacrifice is what made the temple precinct divine. To Cortés and King Charles, it would have meant something very different: that despite their great accomplishments, the Aztecs were barbaric, ignorant of Christianity, and corrupted by the sin of human sacrifice.

Defining a New Nation
How does a new nation define its borders? With rivers and coastlines…with walls and fences…in words and measurements…and in maps. For the American and British diplomats who negotiated the Treaty of Paris, which ended the Revolutionary War and created the United States, the defining map was one first drafted by John Mitchell more than thirty years earlier.

Mitchell, a physician-botanist with no prior mapping experience, could hardly have guessed that his map would one day be used to separate the former colonies from British control. His intent had been quite different: to reinforce British control in North America.

Born into a well-off family in colonial Virginia in 1711, Mitchell had studied medicine in Scotland and spent his spare time on botany. In his 30s, though, his interests turned to the French threat to the British colonies. In the late 1740s, many British colonists thought that the French were ignoring a treaty signed 35 years earlier and were encroaching on British territory between the Appalachians and the Mississippi. To publicize the threat, Mitchell drew a map of all the colonies – for a British public, and from a British point of view. Wherever there was disputed territory, Mitchell assigned it to the British.

Though his first draft was crude, it came to the attention of the British government, which badly needed a large, detailed map of all of North America. The government had the colonial governors send their own maps and boundary information to Mitchell, who published a more detailed and annotated map of the colonies in 1755. Mitchell died in 1768, eight years before the start of the American Revolution.

After the Revolutionary War, when British and American negotiators met in Paris to draft a peace treaty, their most important task was to set the boundaries of the United States. Though the treaty defined those boundaries only in words, the negotiators relied on Mitchell’s map to trace them out. Several versions were outlined: one by John Jay from the American delegation, who traced his understanding of the boundaries, and another by the British negotiator Richard Oswald, who traced the outlines of all earlier treaties. Finally, Oswald added a thin red line, in ink, marking the British interpretation of the new nation – the version that was at last accepted by all the parties.

When the treaty was concluded, Oswald gave this “red line” map as a gift – no doubt a somewhat rueful one – to King George III.

Mapping an Epidemic
It was the last week of August, 1854, when residents of a small, poor, and densely crowded neighborhood in London began to fall ill with stomach cramps, diarrhea, vomiting, and intense thirst. Seventy people died within one 24-hour period; in ten days some 500 lay dead.

It didn’t take long for medical authorities to recognize the disease as one that had killed thousands in Britain in outbreaks in the 1820s and ’40s: it was the dreaded cholera. But stopping the epidemic was another matter, since no one at the time knew what caused cholera or how it was spread. The leading theory, held even by the eminent physician William Farr, one of the founders of epidemiology, maintained that it was miasma, disease carried by poisonous, foul-smelling “vapors.”

John Snow, a pioneering anesthesiologist, thought otherwise. He had treated patients during cholera outbreaks a few years earlier, and was convinced that this was a bowel disease contracted by eating or drinking something contaminated. He strongly suspected the public water pump, since that was how most poor Londoners obtained their water.

Snow combed the neighborhood, visiting some of the homes where people had died and asking where they got their water. The evidence pointed to one source: the Broad Street Pump. When Snow marked the incidence of deaths (which eventually totaled more than 600) on a street map of the area, it was clear that the highest concentration centered around the pump. What’s more, among those who worked at the nearby Lion Brewer (and drank malt liquor rather than water) or in the workhouse (which had its own pump), there were no cases of cholera.

Even before he drew his now famous map, Snow took his theory to the local Board of Governors and asked them to close down the pump. Though they doubted his theory, they agreed to do so, and the epidemic quickly subsided.

Although the cholera bacterium was identified that same year, it was decades before it became widely known. Snow’s map, though, shows that epidemiologic studies can produce successful prevention strategies even without knowing the mechanism of a disease.

How the Earth Works
The first half of the twentieth century wasn’t an easy time for a woman who wanted to be a geologist. But Marie Tharp had luck on her side. When America’s young men went off to fight in World War II, the University of Michigan opened its geology department to women for the first time, and Tharp soon earned a master’s degree. Hired by an Oklahoma oil company, she wasn’t permitted to work with the men searching for oil in the field, and instead was assigned to organize the data and maps they used. In her spare time, she picked up a degree in mathematics.

Tharp was then hired by the geology department at Columbia University – not as a scientist, but as a technical assistant, helping graduate students with their data. She soon found herself working with a short-tempered student named Bruce Heezen. He asked her to take the sonar measurements he and others had made of the depth of the Atlantic and plot them on huge sheets of paper, point by point. As she filled in the data, these two-dimensional maps became three-dimensional landscapes, revealing the details of the ocean floor. She saw the well-known Mid-Atlantic Ridge, a mountain range running down the middle of the ocean floor, following the curves of the continents on either side. But Tharp saw something new in the map: a deep valley dividing the crest of the mountain range.

To her, the rift was a clear sign that the ocean floor was pulling apart as new rock came up from inside the earth – evidence of a theory, advanced by a few geologists, known then as continental drift. In the 1950s, though, a scientist could be fired for being a “drifter,” and Heezen dismissed her findings as “girl talk.” They argued loudly for many months, but as the evidence piled up, Heezen came around. Their first map of the Atlantic was published in 1957.

Tharp subsequently was fired, and although Heezen had become a tenured professor, they were forced to take their work off campus. Over the next twenty years Tharp and Heezen mapped all the world’s oceans from her home. In 1977 they published the “World Ocean Floor,” showing the earth as though all its water had been drained off – and revealing a continuous, 40,000-mile-long ridge girdling the planet. The map remains a tool for geologists studying plate tectonics. As one long-time colleague said, “[Marie] didn’t just make maps; she understood how the earth works.”