It’s been used as currency, incorporated into religious ceremonies, and the cause of political unrest and wars. It’s shaped trade and the formation of cities in unexpected ways. Such has been the influence of this edible rock we call “salt.”

Until a century ago, salt was one of the most valuable substances a person could possess. It was used as money, a way to pay soldiers and laborers. It was one of the first internationally traded goods. Trade routes were built, alliances established, and revolutions stoked over salt. Why has salt been such a precious commodity for us?

At a basic level, salt keeps us alive. Especially in places that are hot and in which people do hard labor, salt lost through perspiration must be replaced.

Salt is a preservative. People used it to keep fishes and meats from rotting, which kept medieval Europe from starvation more than a few times. People in ancient Egypt and China used it to pickle a variety of vegetables. The ancient Chinese saw soy sauce not as a culinary nicety but a vital life source. It maximized the supply of the mineral and combined it with the nutritive goodness of soy.

Salt also led to the domestication of animals. Just like humans, animals rely on salt for their survival. Horses need six times as much as we do; cows, 10 times as much. When people crossed the Bering Strait from modern-day Russia into what is now Alaska 11,000 years ago, they found that animals were drawn to salt marshes and even to salt-rich human urine at the edges of settlements. By luring animals in with salt, these intercontinental migrants were able to domesticate a variety of animals, from dogs and horses to deer and sheep. 

It was actually salt that led to many of the curiously circuitous highways in North America: they came from animals creating paths in search of salt springs, brackish water, or rock salt. Humans broadened these paths as they hunted or sought to domesticate said animals. The paths became wider and increasingly well-established until we ended up with the concrete roads we have today. 

More recently, in 1920, the salt giant Diamond Crystal Salt Company distributed a pamphlet detailing 101 uses for salt. It turns out that salt has far more than 101 uses, but here are some that Diamond Crystal highlighted:

-bringing out more color in boiled vegetables

-making ice cream

-subduing grease fires

-making cut flowers stay fresh longer

-killing poison ivy

-removing stains

-alleviating sprains and sore throats

-augmenting heat in boiling water

Another use not mentioned in the booklet is deicing roads. The United States is the biggest producer and consumer of salt, but little of it is culinary. 51 percent of the salt produced is for deicing streets. It’s also used in numerous pharmaceuticals, fertilizers, soaps, and baby formula.

The notion of killing over a compound that most people have in their kitchen sounds almost laughable today. People from any given era (including our own) have the tendency to place tremendous value on the goods that are prized in their own time. No doubt posterity will view some of our own preoccupations with similar bemusement.

Humans have a long-standing, peculiar obsession with salt that extends beyond the concrete. The poet Homer called salt a “divine substance.” Plato believed it was particularly beloved of the gods.

Around the world and across history, salt is associated with fertility and sexual potency. In ancient Rome, a man in love was described as salax, or “in a salted state.” It is from this word that we get the word “salacious.” In wedding ceremonies in the Pyrenees Mountains, married couples went to church with salt in pockets to prevent impotence. In Germany, someone would cover the bride’s shoes with salt. Celibates in Egypt would avoid salt because it awakened sexual desire.

In medieval Paris, there was a poem about wives salting their husbands to make them virile: “With this salting, front and back/ Strong natures they will not lack.” Anglo-Saxon farmers would use salt in their farming rituals as they plowed the fields and prayed to the earth goddess for a generous yield.

Salt has become connected to sexual appetite and fertility, but it’s also considered a terrific way to demon-proof homes and places of business. In traditional Japanese theaters, salt would be strewn across the stage before performances to protect actors against demons. In Haiti, salt resurrects zombies. In Africa and the Caribbean, there are some women who shed their skin at night and move around as balls of fire—a phenomenon that can only be curtailed by covering them in salt. Jews and Muslims both ward off the evil eye with salt. In Ezekiel 16:4, the author writes of covering infants with salt as a form of care and protection. Until the 1400s, infants in France were rubbed down with salt until they received baptism.

 Over a century ago, one Jungian psychologist interpreted humanity’s odd (and to his mind, unwarranted) preoccupation with an insignificant things like salt as an unconscious association with something that’s of actual importance: fluids like semen and urine, which both contain salt. But salt is in blood, sweat, and every vital organ of the body as well. Water is not enough: Our cells require salts in order to stay hydrated.

Salt featured prominently in China’s history. It was there that the first war over salt was fought. In the northern province of Shanxi, amidst deserts and arid plains, was a salt lake that would dry up every summer, allowing the local inhabitants to collect salty crystals from the lake’s basin. There was constant warfare over ownership of the lake, dating back to 6,000 BC or later. There are written records dating back to 800 BC which describe the production of salt in China, a process that involved boiling water in clay jars, which then changed to iron pans around 1,000 BC.

In the centuries following Confucius’ death in 479 BC, China was a chaotic mess of warring states. China eventually became a unified nation, but throughout the unification process, salt was at the heart of political debate. Many ancient Chinese politicians taxed salt as a way of raking in wealth for the state. This connection between salt and government is found in the ancient symbol for salt, yan. The character is comprised of several smaller pictures: a tool, a government official, and brine. The very written word saw salt production as a state-run affair.

For about 600 years, beginning the first century AD, a more Confucian-influenced minister broke up the government’s salt monopoly, deeming it imprudent for the government to compete with its subjects for profit. Eventually, the monopoly reemerged, and one of the ways that aristocrats displayed their wealth was by serving salt in a small platter at mealtimes. What constituted opulence a millennium ago is now a commonplace in China and most parts of the world.

The Basques have peopled the mountains of modern-day Spain and France along the northern Atlantic coast for well over a thousand years. To this day, they remain proud of their heritage and culture, and are still removed from the many winds of trysts and wars that often battered their close neighbors. When the Romans, Celts, and Vikings swept through large swaths of Europe, the Basques emerged largely unscathed. Even their native tongue is utterly distinct, outside the Indo-European language family back to which almost all Europeans trace their lingual roots. 

The Basques are believed to be the world’s first whalers. There are bills of sale listing units of whale oil dating to 670 AD. Demand for whale oil and teeth made the Basques wealthy, and as Europe entered the Middle Ages, so did whale meat and blubber.

Catholic Europe was becoming particularly stringent regarding fasts. Catholics were to abstain from meats during the Lenten Fast, which lasted for the 40 days leading to the crucifixion and resurrection of the Christ. Eventually, it wasn’t just the 40 days preceding Easter, but every Friday that Catholics could not eat meat. These so-called “lean days” were strictly enforced. In England, breaking fast was punishable by hanging. Sex was also forbidden on such days and abstinence from red meat went along with that as it was considered “hot” and could excite the passions at inopportune moments.

Animals captured from the sea, however, were considered “cold” meats, rather than hot, and were therefore acceptable vittles during fasts. Porpoises, whales, beavers, and otters were fair game. Only the wealthy could afford the choicest cuts, and the poor contented themselves with lard de carême, literally “lent blubber.” These fatty portions were cured with salt and enjoyed by the hovelled riff-raff.

 By the 800s, the Vikings had become a competitor of the Basques, but not outright antagonists, like they were to the rest of Europe. The Vikings had a port on the coast of the Basque’s northern territories, and through this proximity the Basques learned to replicate the Viking vessels that were prized for their speed. These new vessels allowed the Basques to do more than hunt whales in the bay—the ships could take them hundreds of miles from home. The newfound mobility led to the discovery of a sea dweller far more lucrative than the whale: the Atlantic cod.

The bottom-dwelling Atlantic cod had a lean white meat that kept far better than the oilier, darker meat of Mediterranean fish, like herring and anchovies. Fattier fish rot more quickly, and the excess oil also makes it difficult to work in the preserving salt. It was sufficient to simply cover the cod in salt.

The rest of Europe was in a frenzy to break into the salt cod market, but the Basques were optimally positioned. Even their Viking competitors could not keep pace, because geography was not in their favor. They developed an ingenious method of salt production which drew salt from artificial ponds that were shallow enough to evaporate, leaving the precious salty residue. But there was far more sunshine in southern states like Spain, and so salt production began to take off in regions closer to the Mediterranean. Thus, a web of trade routes formed in which Basque became the node between the cod-rich northern seas to the salt-rich southern regions. 

Unlike traditional fishing, in which anglers would bring a modest catch to market as quickly as possible, the artificial salt pond model and the enormous amounts of salt it produced enabled the Basques (and eventually other European nations) to return from long voyages with enormous loads of preserved fish to cities and townships across the continent. And because supply went up, the prices dropped to levels that made cod affordable even for peasantry. Between the 1500s and the 1700s, daily salt intake among the common folk rose from 40 grams to 70 grams—largely due to salted fish. It’s not a long shot to submit that these developments saved regions of Europe from widespread famine.

Unbeknownst to most people, “Mahatma” was not Gandhi’s first name. Mahatma was an title given to him by the famous Bengali poet, Tagore; it literally means “great soul.” Gandhi was born Mohondas Karamchand Gandhi in 1869. He grew up in the age of the British Raj, when the East India Trading Company and then the Crown oversaw management of the subcontinent and its assets. One of the trades that the British took control of was salt. It was a major source of revenue for the British and was used as currency in many provinces.

 After studying in London and then South Africa, and doing jail time in the latter for advocating for India’s liberation, Gandhi returned to India and became the face of India’s liberation. His travels and studies informed his philosophy of resistance. He settled on satyagraha, or “the force of truth.”

 Salt featured prominently in India’s independence from the British. On March 2, 1930, Gandhi wrote to the viceroy of India, Lord Irwin, declaring his intention to march to the sea and collect his own salt instead of supporting the British monopoly. Gandhi chose this salt satyagraha as a key element of his liberation campaign because salt was a basic need of everyone in India, regardless of religion or caste, rich and poor alike. On March 12, 1930, Gandhi led a group of 78 from his ashram on a 240-mile march to the sea in western India. All along the way, he invited others to join him. At the end of the 25-day march, Gandhi and a thousands-strong multitude arrived at the beach. Together, they defied British law by reaching down and picking up handfuls of salt crystals in the famous Rann of Kutch marshland, just as Indians had done for over 5,000 years.

A day later, crowds in the eastern state of Orissa did the same thing. There were unapologetic displays of civil disobedience all along the eastern coast. The prisons were full and the police beat numerous people, but the masses could not be dissuaded. Gandhi was prepared to be the only person to march for salt, but his actions were the catalyst for a national protest movement that the British could not quell.

When the first prime minister of an independent India, Jawaharlal Nehru, was asked what he thought of the late Gandhiji (“ji” is a term of respect like “sir”), Nehru replied that he would always have the image of a thin man, bamboo staff in hand, leading the masses toward the Dandi Beach to collect sea salt.