Detroit's salt mine: City beneath the city

Miners work deep underground in this undated photo. A huge sea covering the region evaporated more than 400 million years ago, forming salt deposits that were gradually buried by glacial activity.

The existence of rock salt in the Detroit area was discovered in 1895, and the difficult and expensive work of digging a mine shaft began in 1906. The original company went bankrupt before any salt was mined. The reorganized Detroit Rock Salt Co. opened in 1910. Its facility on W. Fort at Sanders is seen in 1923.

A worker toils in the salt mine in January 1924. By then the mine had been bought by the International Salt Co.

By 1914, the huge Detroit mine was producing 8,000 tons of rock salt each month. This mine passageway, seen in 1941, was 22 feet wide.

A miner operates a lump drill in April 1945. In the mine’s early days, the salt was used mainly in the leather and food processing industries. In recent years, the salt has been used exclusively for deicing roads.

Marcus Maynarich, one of the two shot loaders at the Detroit mine, loads powder into holes in April 1945. An average of 10 sticks of dynamite is loaded into each of the holes, or about 130 pounds of powder to each room. An average of five rooms a night were blasted in that time.

A group of miners wait at the time clocks to go to work in April 1945. They carry the common type of carbide miners lamp.

Miners load salt on a conveyor belt in August 1950.

Miners use an electric shovel in August 1950. All equipment was lowered into the mine via a shaft. Due to the shaft’s narrow opening, most equipment is disassembled and lowered piece by piece, then reassembled in a machine shop below.

A traffic sign is seen in the salt mine in August 1950.

Michigan Gov. G. Mennen "Soapy" Williams, left, and others view the mine in 1950.

Gov. Williams, at lower right, tours the salt mine in October 1950.

A tour at the International Salt Mines, 1950.

A Jeep pulls men from the shaft bottom over roads of pure salt in the Detroit mine of the International Salt Co. in Detroit, in October 1950.

A sinkhole developed under the Windsor salt mine, across the river from Detroit, in 1954, causing thousands of dollars in damage.

Rock salt is picked up by a power shovel circa 1957.

International Salt Mine in Detroit, December 1965.

Harvey Ward and Leslie Walker work on a salt pile in October 1953.

Joseph L. Visintainer uses a power saw that undercuts a 10-foot "room" of salt, circa 1957. Under the room-and-pillar method of removing salt, shafts were sunk into the ground, and miners broke up the rock salt with drills after detonation engineers had blasted a section.The miners then removed chunks of salt, creating huge rooms separated by pillars of salt.

Russell M. Burrows and Craig Hotson work in the mines in June 1967.

John L. Ryan Jr., assistant plant manager, and Roy W. Yokley, mine foreman, on the phone, work in the mine circa 1957.

A trailer serves as an office in the salt mines in 1967.

A mountain of salt is reflected in water at the Morton salt yards at Fort and Miller in 1972.

A front-end loader digs into a salt pile at the Morton yard in February 1977.

Rock salt processing in December 1974.

A truck, traveling on smooth roads of glittering salt 1,137 feet beneath Detroit in the mine of the International Salt Company, carries newly blasted salt several thousand feet to a primary crusher station in this undated photo.

The salt deposit is a comparatively flat seam averaging 26 feet in thickness in this undated photo.

Salt is conveyed to the surface from 1,200 feet below ground in 1982.

The salt mine is seen in 1982, a year before International Salt closed the mine's operations.

Mining at the International Salt Mines in the early 1980s.

In 1985, Chrystal Mines, Inc. purchased the mine, intending to use it as a storage site.

A ship unloads salt at the Detroit Marine terminal, November 1983.

Dennis Gilmore of Dallas, Texas, was visiting friends in Detroit and took a 60-70 pound saltblock home with him during a tour of the mines in April 1986, when they were owned by Crystal Mines, Inc.

Walter Tomyn, owner of what was then Crystal Salt mines, poses for a photo in 1986. In 1997, the Detroit Salt Company LLC purchased the mines from Crystal and began production in 1998. In 2010, the Kissner Group purchased Detroit Salt, along with ownership of the mine.