What Lies Beneath

Nearly 1,200 ft. below Detroit, workers excavate one of the continent's robust salt reserves

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Lisa Kereszi for TIME

A giant salt mine tunnel.

Detroit is known for cars and music. Natural resources? Not so much. Yet each day, 30 or so miners descend nearly 1,200 ft. beneath the city to extract salt from remnants of ancient seas that extend below much of the Great Lakes — and form one of North America's robust salt reserves.

The use of salt to season and preserve food dates back at least 8,000 years. It has been used by Egyptians in burials, by the Catholic Church in baptisms, by Hindus in weddings and by Jews in housewarmings. "God sent down four blessings from the sky," the Prophet Muhammad said. "Fire, water, iron and salt." In the 1800s, Michiganders began digging deep wells to pull salt for tanning leather and preserving food. The city's location on the Detroit River near Lake Erie made it a prime platform for delivering salt to the East Coast and across the Midwest.

In 1906, a group of investors formed the Detroit Salt Co., which today manages some 5 miles of tunnels beneath the city. Typically, miners work 10-hour shifts using a machine called a continuous miner to scrape salt off the walls into bins; the salt is hauled away for processing and sold to local governments for snow removal. Salt isn't a high-profit industry. But history and faith link it to good luck, something this city could always use.

For more stories from Time Inc.'s Assignment Detroit project, go to time.com/detroit