Old Copper Complex is a term used for ancient Native North American societies known to have been heavily involved in the utilization of copper for weaponry and tools. The evidence of smelting or alloying that has been found is subject to some dispute and a common assumption by archaeologists is that objects were cold-worked into shape. Artifacts from some of these sites have been dated from 4000 to 1000 BCE. Furthermore, some archaeologists find artifactual and structural evidence of casting by Hopewellian and Mississippian peoples to be demonstrated in the archaeological record.
The Old Copper Complex of the Western Great Lakes is the best known of these. Great Lakes natives of the Archaic tradition located 99% pure copper in the area of Lake Superior, both in veins and nuggets in gravel beds. Major quarries were located on Isle Royale, the Keweenaw Peninsula, and the Brule River, and copper was deposited elsewhere by glaciation as well. Eventually they learned to hammer the copper and produce a variety of spearpoints, tools and decorative objects. In addition to practical use, the Copper Complex peoples traded copper goods to obtain other exotic materials.
The Copper Complex can be dated as far back as 6,000 years. By about 3,000 years ago the use of copper is increasingly restricted to jewelry and other status-related items, rather than for tools. This is thought to represent the development of more complex hierarchical cultures in the area.
The Copper Culture State Park, in Oconto, northeastern Wisconsin contains an ancient burial ground used by the Old Copper Complex Culture of early Native Americans, here between 5,000 and 6,000 years ago. It was rediscovered in June 1952 by a 13-year-old boy who unearthed human bones while playing in an old quarry. By July the first archaeological dig had commenced, as part of the program of the Wisconsin Archaeological Survey.
Copper is known to have been traded from the Great Lakes region to other parts of North America. However, there were also other sources of copper, including in the Appalachian Mountains near the Etowah Site in Alabama. The Mississippian copper plates were made by a process of annealing the copper. Copper can also be found in Manitoba, along with old copper artifacts found at various locations. Evidence of mining, deep holes chipped into the rock, can be found in Ontario, Manitoba, and around Lake Superior. The artifacts are found over a very wide range, all around the Great Lakes region, and far south, into what is now the USA.