Having a shaker full of salt in almost every house on Earth today is a privilege that would have completely blown our ancestors minds.

That’s because salt is one of the most important substances to life on Earth.

To find out why we need to look at what salt actually is. Salt is a molecule made of a sodium and a chlorine atom joined together with an ionic bond.

As a quick recap, an ionic bond happens when an atom donates an electron to another atom. This gives the first atom a positive charge and the second atom a negative charge, and they are both now called ‘ions’. The different charge makes the ions attracted to each other, and millions of them stick together in a big crystal-shaped lattice.

A salt rock is one big crystal lattice. Green is chlorine ions, purple is sodium ions.
A salt rock is one big crystal lattice. Green is chlorine ions, purple is sodium ions.

This attraction holds salt crystals tightly together. You can heat it, smash it, or burn it but much more than other substances, salt holds together.

That is, unless you give the ions something that is more attractive to them than each other.

Salt is easily seduced by water. As another quick recap, water has a special property called ‘polarity‘ that makes its molecules irresistable to lots of ionic molecules. As soon as salt touches water, the ions split off and float around – or ‘dissolve’ in the water.

All animals need sodium ions about as much as they need food and water. It’s crucial for moving our muscles, for generating nerve impulses so we can feel things, and for regulating blood pressure.

Because of how it dissolves, salty water is a perfect way to transport those crucial sodium ions through our bodies.

If you don’t have enough sodium ions in your body at all times, your brain swells, you fall into a coma, and die.

On the other hand if you have too many, they will pull water out of your cells like air in a vacuum-sealed bag, which unwinds all of your important proteins. This is bad news and if it happens in your brain you’ll have a stroke.

Living things that don’t have skin like snails, slugs, leeches, and bacteria, are especially vulnerable to too much salt. If they are exposed to it, it will dissolve into their bodies, unwind their proteins and kill them.

This is why we salt our meats and other food as a form of preservation; it kills the vulnerable bacteria. Our ability to preserve food in this way has been called a “founding contributor to the development of civilisation.”

Pretty big deal.

Keeping the right balance of salt isn’t easy. Our body is constantly losing it through bodily functions, and it must always be replaced. But it’s not easy to get, particularly if you live inland or far from a salt flat.

Salt flats are usually the remnants of saltwater lakes, now evaporated. This is Salinas Grandes, Argentina. Image source: Kevin Jones
Salt flats are usually the remnants of saltwater lakes, now evaporated. This is Salinas Grandes, Argentina. Image source: Kevin Jones

Carnivores are usually fine as they just let the animals they eat deal with the problem. But herbivores and omnivores need to supplement their diets. This is why we need to give our pet rabbits, horses, and cattle salt licks to stay healthy, but not our cats and dogs.

But if you’re a large inland herbivore like an elephant, you may have to travel vast distances to salt rich clays or rocks, or venture deep into underground caves.

Throughout human history, hunter-gatherer tribes generally did not require salt supplementation as their diets were rich in meat.

On the other hand, settled societies who tended to be more reliant on vegetables and grains, went crazy over salt.

Let’s have a quick look at salt as it appears in the historical record:


  • Salt was the subject of the first tax in history, which was in Ancient China. Revenues from a later version of this tax paid for the Great Wall, and sustained successive dynasties for thousands of years. At times tax on salt brought in half of the ancient empire’s tax revenue.


  • The French revolution was in part motivated by an extremely high and unpopular tax on salt, called the gabelle, which disproportionally affected the poor.
  • The Indian independence movement was in part motivated by high salt taxes imposed by the British Raj.

Trade and infrastructure

  • Salt production was one of the original human industries.It was one of the first international commodities, with merchants creating salt routes across the Sahara and Mediterranean Sea.
  • The first great Roman road to be built was the Via Salaria, or ‘Salt Road’, built for the purpose of transporting salt across the Italian Penninsula. It was eventually extended to run 242 kilometers.
  • ‘Salt Roads’ traversed Europe throughout much of the Middle Ages, and many modern highways were built on top of them.


  • The oldest settlement in Europe, Solnitsta in Bulgaria, was built around a salt production facility and supplied salt to people living in the Balkans.
  • Rome was built where it was in part because it was next to a saltwork site and a river.
  • Munich, Germany was built along one of Europe’s salt roads, and flourished as a result of a salt tax.
  • In the 19th Century, salt mined in Cheshire, UK was brought to the nearest port, called Liverpool, before being exported globally. It transformed Liverpool from a small port to a prime city.
  • Timbuktu, Mali was famous as a market city for salt, gold, ivory, and slaves for centuries.
  • Salzburg, Austria. Salzburg means ‘Salt Castle’ and it sits on is the Salzach River, or ‘Salt River’, both references to the nearby salt mines and the river on which salt barges have travelled since the 8th Century.
  • Tuzla, the third largest city of Bosnia, was built on a salt mine (Tuzla meant ‘salt mine’ in Ottoman Turkish). Because of past excavations, parts of the city are now sinking into the ground.
  • Every city in Britain that ends in -wich, like Norwich, was once the site of a salt water spring used for salt production.


  • Poland’s salt mines in part contributed to its 16th Century golden age, until disrupted by German innovations in sea salt production.
  • Venice rose to prominence in part because it secured a salt monolopy over the Mediterranean, which it traded in Constantinople for exotic spices until disrupted by salt production in the newly discovered Americas.


  • War of Ferrara, Italy (1482-4) was in part caused by disputes between Venetians, who had a commercial monopoly in the salt trade, and the regional Ferrara, who sought to break it.
  • The Salt War, Italy (1540). Heavy taxation of salt in the free commune of Perugia by the Papal States sparked an insurrection called the Salt War.
  • During the American Revolutionary War, Loyalist forces regularly attacked Revolutionaries’ salt shipments in order to interfere with their ability to preserve food.
  • San Elizario Salt War, Texas (1877-8). An armed dispute between Anglo Texan capitalists and Mexican and Tejano people over control of immense salt lakes near El Paso.
The ‘Salt Castle’ Salzburg has greeted salt barges travelling on this river for centuries. Photo by Reinhard Kraasch
The ‘Salt Castle’ Salzburg has greeted salt barges travelling on this river for centuries. Photo by Reinhard Kraasch

The salt on our tables is something that we take for granted, but it’s a commodity that has shaped cities and empires.

Today it’s a product of a hugely complex global economy that is able to deliver what we need, regardless of how far we are from the ocean or from salt flats.

Additional notes