Detroit’s 100-Mile Underground Tunnel That Few Have Seen

There are plenty of cities across America that sit on top of a massive network of tunnels. Not including the thousands of yards of sewage and water pipes, cities like New York City with its massive subway system, or Las Vegas and its massive flood control tunnels that thousands of residents live in below the city.

Everyone knows Detroit as the Motor City, but there's another secret hiding over one thousand feet beneath the surface. Below the city of Detroit is a massive network of underground tunnels that have been actively used since 1895. The purpose? Salt.

⬇️INSIDE MICHIGAN'S DEEPEST CAVE⬇️

Detroit Salt Mines

Now, as someone who was born and raised in Michigan, I struggle to understand if I have just completely missed something obvious or if the Detroit Salt Mines are a largely underrated component of Michigan. Either way, the mines are a feat of modern engineering that should be highlighted.

In the year 1895, rock salt was discovered in the Detroit area. This rock salt formed some 400 million years ago, but it wasn't until 1906 that a company, the Detroit Rock Salt Company, tried mining it. In 1910, a 1,060-foot shaft was dug under the city, and within 5 years of the mine opening, it was removing 8,000 tons of rock salt a month. 

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The technique for mining today is very similar to how it was in this 1960 video about the mine. Holes are made in the rock salt, dynamite is placed inside, and over a thousand tons can be blown from the face and transported to the surface. Interestingly, the shafts are so small that most of the equipment had to be brought down piece by piece and built in the mines themselves.

The mine served the leather and food processing industries for most of the 1900s until it closed in 1983. It reopened in 1998 to instead focus on mining for road de-icing salt. It is now the only product made from the mine. To date, the mine is approximately 1,500 acres large, has 100 miles of roads,  and produces 1.7 million tons of salt annually as of 2017.

Tours of the mines used to take place back in the 80s, but since the mines reopened around the turn of the century, citizen access has been largely restricted. Ultimately, the Detroit Salt Mines may be Michigan's biggest secret.