Salt is taken from mines such as this one
Salt is one of the most ubiquitous natural substances in the world. As a species, we consume tons of the stuff each year. It is obtained in two ways: one way is by harvesting salt from the sea, and another is by mining it.
The mineral is plentiful today, but before the Industrial Revolution, it was harder to retrieve. Mining for salt was one of the most dangerous jobs because of how rapidly dehydration in the miners occurred and the many issues caused by excessive sodium intake.