1923If you doubt that metro detroiters are “the salt of the earth,” just look down — about 1,200 feet. In the city’s cellar are more than 1,400 acres of a salt mine, remnants of what was a sea millions of years ago. The men wearing headlamps here are using pickaxes to hack at salt rocks. The mineshaft’s opening is on Sanders Street on the west side of Detroit, and the maze runs beneath Dearborn’s Rouge complex, Melvindale, and Allen Park. Opened in 1896, the mine was operated for years by the International Salt Mine Co. until 1983, when it closed. But the mine reopened in 1997, when the Detroit Salt Co. assumed ownership, supplying Michigan and other states with rock salt to melt hazardous ice on winter roadways. In 1940, Detroit became the first major city to use rock salt to control snow and ice.