Detroit’s salt mines are located right beneath the city—they’re basically another city. The mines cover 1500 acres and nearly 100 miles of underground roads.
They stretch from Dearborn (aka Henry Ford’s birthplace) via Melvindale to Allen Park in the southwest of the city. How did the salt get there?
Around 400 million years ago, an area called the Michigan Basin was separated from the ocean and kept sinking lower and lower and filling with salty ocean water.
The water eventually evaporated and left large salt deposits behind. The Detroit Salt and Manufacturing Company operated the mine until 1983 when falling salt prices forced them to close. The mine had its heyday in the 1920s, 1940s and 1950s.
During the time, it was open to the public with guided tours. Today the entrance to the mine at 12841 Sanders Street is only open to delivery trucks. Tours have not been given since the 1980s.