On May 17, 1881, Julius Ropes, a Marquette chemist and geologist, struck his exploring pick into some moss-covered rock near Ispheming, analyzed it, and discovered that it contained gold. Two years later, Ropes opened a mine, the only gold mine east of the Mississippi River, and hauled out $703,000 worth of gold and silver before labor disputes forced him to close in 1897.
Source: Mich-Again’s Day.