تعدين النحاس في مشيگن
The Michigan State Geologist Douglass Houghton (later to become mayor of Detroit) reported on the copper deposits in 1841, which quickly began a rush of prospectors.. Mining took place along a belt that stretched about 100 miles southwest to northeast through Ontonagon, Houghton, and Keweenaw counties.:16–17 Isle Royale, on the north side of Lake Superior, was extensively …
WhatsApp: +86 18221755073