The ancient copper of Isle Royale

Genuine 4,500-year-old Indigenous copper mining, and the myths built on it

Isle Royale lies in the northwest of Lake Superior, 45 miles long and 9 wide, closer to Ontario than to Michigan, with no roads and no permanent residents. The Ojibwe call it Minong. Its ridges are ancient lava flows, the Portage Lake Lava series, folded into the same basin whose other edge forms the Keweenaw Peninsula, and both carry something rare in the world: copper so pure it can be found as solid metal in the rock.

People found it soon after the glaciers left. The National Park Service dates Indigenous copper mining on the Keweenaw to as early as 8,000 years ago and on Isle Royale to around 6,500 years ago, though it puts firm evidence at Minong at no less than 4,500 years; either way these are among the oldest metal mines anywhere. The miners beat the raw metal free from the bedrock with rounded beach cobbles, leaving pits and trenches across the island, some up to 70 feet deep, and the hammerstones lying in them. The Minong Ridge and McCargoe Cove hold one of the largest concentrations of Indigenous mining pits ever found, and by far the most thoroughly studied.

The copper had power beyond its use. People of Lake Superior carried small pieces in their medicine bags, wrapped and handed down from father to son, and in 1670 a Jesuit missionary named Dablon wrote of "an island called Menong, celebrated for its copper." When the 19th-century surveyor Charles Whittlesey mapped the old pits, he credited them to an ancient people of whom history gave no account, and the mystery invited all kinds of guesses about who they were. The archaeology is clear that every precontact artifact from the Keweenaw and Isle Royale is Indigenous in workmanship and style, made by the ancestors of today's American Indians, and oral tradition agrees.

The ancient workings guided the miners who came after. A report by Douglass Houghton, Michigan's first state geologist, set off a copper boom in the 1840s, and prospectors found stone hammers and half-worked copper wherever they dug; the old pits led them to many of the deposits they opened. The Minong Mining Company later worked the ridge, but the island's remoteness and thin veins doomed most of the mines, and mining ended in the 1880s.

Isle Royale became a national park in 1940, and its 1931 founding law singled out the Indigenous mines. In 2021 the Minong Copper Mining District, more than 200 acres in designated wilderness, became a National Historic Landmark. The pits and everything in them are protected.