It is one of the most abundant substances on Earth, was once used as currency and costs politicians their jobs if there isn't enough.
Salt, the ubiquitous substance that helps clear our highways of snow, is mined in a half-dozen states from deposits formed when the oceans that covered the continent receded 500 million years ago, leaving behind the salt from the water.
Used by the Romans to pay soldiers, the compound known as sodium chloride has helped clear snow from the roads in New England since the 1940s and has been a necessary weapon in the nation's war on winter for 40 years.
Despite the damage it causes to concrete, pavement, sidewalks and waterways, we use 16 million tons of it on highways nationwide each year.
Each fall, the state of Maryland stocks 230,000 tons of salt - enough to fill about 30,000 dump trucks - transporting it by truck from ships unloaded at the port of Baltimore to salt domes and cavernous storage barns across the state.
It is a chemical people hate on their cars, but demand on their roads. And shortages can be politically devastating.
The late Michael A. Bilandic was defeated in his bid to be re-elected as mayor of Chicago in 1979 shortly after he failed to sufficiently salt the city's roads during a blizzard. Shortages of salt for Baltimore County's roads in early 1994 were largely seen as contributing to the defeat of County Executive Roger B. Hayden later that year.
There are alternatives for melting snow and ice. But salt - specifically sodium chloride - is the most widely used for three reasons: chemistry, cost and climate.
Most snow in the United States falls when the temperatures are between 25 and 32 degrees Fahrenheit, which makes salt an ideal compound for winter because it works until temperatures drop to minus 6 degrees, a level at which salt itself will freeze.
In places such as Alaska, Canada, and the Upper Midwest, where temperatures frequently dip to subzero levels, highway crews often lay off the use of salt altogether because the weather is too cold for it to work.
Crews in such frigid areas repeatedly plow to keep the roads as clear as possible of moisture and when a lot of snow accumulates, they sometimes spread sand and crushed stones, which cannot melt snow but will increase traction.
"When you get down to zero degrees, or 10 below zero, the best thing to do is just make sure the roads are as clear as possible," said Bruce Beltram of the Salt Institute, an agency that represents salt wholesalers and dealers.
