The mystery of who mined massive copper deposits along the shores of Lake Superior more than 5,000 years ago has provided the fuel for many outlandish tales. Wisconsin Historical Society

In the summer of 1952, 13-year-old Donald Baldwin was dig­­ging around in an old gravel quarry near Oconto, Wisconsin, when he unearthed a pile of human bones. Thankfully, archaeologists were called to the scene rather than the local police, as young Donald had found an ancient burial ground. The skeletons, buried amid copper artifacts, turned out to be the earliest evidence of an ex­tensive, ancient trading culture based heavily on copper mined on the Keweenaw Peninsula and Isle Royale, along the shores of Lake Superior.

But ever since, figuring out who mined this copper – and how – has been the base for wild historical speculation. Amateur historians argue that the Lake Superior copper was mined during the same period as the European Bronze Age, with their rough estimates suggesting that 1.5 billion pounds of copper was mined from the region, far more than seems to have been used by the native peoples.

Could it be possible that ancient Europeans came to North America to mine the copper and bring it back to Europe? Imagine ancient Phoenicians and Norse Kings crossing the Atlantic in flotillas weighed down with New World copper.

There are rumours of a Menominee tale from Wisconsin of light-skinned men mining the copper from nearby Lake Superior. Further north near Peterborough, Ontario, a large, flat stone appears to have been engraved with a pre-runic alphabet that some suggest was used by the ancient Norse. Could it be evidence of the Norse King Woden-lithi, who some say travelled to North America in 1700 BC to establish a copper trade?

Could Baltic and Celtic ships have also made unrecorded voyages? There are stories of English explorers coming across a native tribe with blond hair and blue eyes, speaking a language that carried a hint of Gaelic. Are these the descendents of the Welsh prince and explorer, Madoc, who, according to folklore, sailed to North America in AD 1170?

Not even the Ojibwe know who originally mined the copper on their territory, which only fuels speculation. The Ojibwe migrated into the region long after the mining is said to have ceased, discovering the abandoned copper pits when they arrived.

Who, then, was this “unknown race of people” who originally mined the copper? Could it have been ancient ­Europeans? If you put that question to a professional archaeologist, he or she would give you a short answer: No.

No rock hieroglyphs have been linked to an ancient Nordic language by an archaeologist, no blond-haired, blue-eyed tribes have turned up, and the “unknown race” was likely just another migrating native group. In fact, no evidence of an ancient European presence (Norse or Phoenician or otherwise) has ever turned up at an archaeological site in North America. As for the ancient copper pits, more careful estimates suggest that less than 1.5 billion pounds of copper was mined, and that the mining activity ended 2,000 years before the European Bronze Age, which began roughly 5,000 years ago.

This, however, only makes the industriousness of the ancient North American miners all the more impressive. Using little more than stone hammers and hatchets, they extracted enough tonnes of copper to support a trading network that spread over much of the continent. Lake Superior copper has been found as far west as the Rocky Mountains, as far north as the Arctic, and as far south as Louisiana.

The region’s copper was almost entirely pure, making pre-industrial extraction possible. The ancient miners dug around 5,000 pits, some with five-metre deep shafts that included some tunnelling. We know very little about ancient mining techniques though, as most sites were destroyed when modern mine developers used the ancient pits to determine the best locations for building their own operations.

The ancient miners chipped away nuggets, preferring pieces small enough to form with just a stone hammer. Other pieces were flattened into sheets through repeated hammering. The copper was made more malleable when heated over fire. They shaped the nuggets into various tools and weapons like knives, spear points, fishhooks, chisels, wedges, awls and clasps, and decorative objects like beads, bracelets and rings. Copper also likely held a spiritual significance, and a reverence for both the metal and the ore deposits continued with the Ojibwe, who also made use of copper for hunting and fishing purposes.

Although many questions surrounding Lake Superior’s prehistoric copper mining mystery remain, it is a story of ancient ingenuity worthy of modern admiration.