Here’s a chart from this neat article on the history of salt de-icing on US roads. It all started in New Hampshire, but you can see the growth of de-icing salt (the green line on the chart):
As the article explains, all this salt has a bit of an impact on the local nonhuman environment:
Just as alarmingly, when that salt dissolves and splits into sodium and chloride, it washes away into rivers and streams. Chloride, in particular, doesn’t get filtered out naturally by soil and accumulates in waterways. In December 2014, a study by the US Geological Survey found that chloride levels were on the rise in 84 percent of urban streams studied — with 29 percent exceeding federal safety limits of 230 milligrams per liter for at least part of the year.
But it’s an even bigger deal for all the other freshwater organisms in those lakes and streams. As Nina Rastogi reported for Slate in 2010, high chloride levels interfere with the ability of amphibians to regulate how fluids pass through their permeable skins. Extra salinity can also affect oxygen levels and create dead zones in lakes. The extra chemicals added to road salt can cause fish die-offs. And the salty soil near roadways can kill trees and other plants.
Perhaps the most unexpected effect comes with land animals. Moose, elk, and other mammals often visit natural salt licks to fill up on sodium. But during the winter, they often wander up to salted roads instead — raising the chances of crashes and roadkill.
Something to keep in mind as you drive around the Twin Cities in the wintertime.