Within the state of Michigan, copper is found almost exclusively in the western portion of the Upper Peninsula, in an area known as the Copper Country. The Copper Country is highly unusual among copper-mining districts, because copper is predominantly found in the form of pure copper metal (native copper) rather than the copper oxides or copper sulfides that form the copper ore at almost every other copper-mining district. The copper deposits occur in rocks of Precambrian age, in a thick sequence of northwest-dipping sandstones, conglomerates, ash beds, and flood basalts associated with the Keweenawan Rift.

The most conclusive evidence suggests that native copper was utilized to produce a wide variety of tools beginning in the Middle Archaic period circa 4,000 BC. The vast majority of this evidence comes from dense concentrations of Old Copper Culture finds in eastern Wisconsin. Old Copper Culture 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. It is to be distinguished from the Copper Age (Chalcolithic era), when copper use becomes systematic.

These copper tools cover a broad range of artifact types: axes, adzes, various forms of projectile points, knives, perforators, fishhooks and harpoons. By about 1,500 BC artifact forms began to shift from utilitarian objects to personal ornaments, which may reflect an increase in social stratification toward the Late Archaic and Early Woodland period (Pleger 2000). While copper continued to be used in North America up until European contact, it was only used in small amounts, primarily for symbolic ornaments. At the turn of the twentieth century, Mr. P.V. Lawson of Menasha Wisconsin, compiled the most comprehensive inventory of Old Copper in the state, estimated to be at least 13,000 copper artifacts (Brown 1904:50). In the one hundred years since this initial tabulation, it is difficult to assess the total number of Old Copper artifacts so far discovered, however it quite possibly could be in range of 20,000. Evidence suggests that the total number would have been much greater if early European pioneers had not melted down this valuable metal to forge new articles of material culture

Donald Baldwin (left) with local officials examining the ancient burial at the Oconto site in 1952.

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 during the Copper Age. It was not until the development of radiocarbon dating in the 1950s that the first conclusive evidence of the age of the Old Copper Complex in Wisconsin was realized. These results provided conclusive evidence that aboriginal use of Great Lakes copper began during Middle Archaic times, circa 4,000 B.C. It was rediscovered in June 1952 by a 13 year old Donald Baldwin 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.

The broad distribution of the Old Copper Complex is invariably the result of trade throughout the Great Lakes region. For instance, it has been noted there is a close burial pattern and material culture resemblance between the Oconto cemetery in Oconto county Wisconsin and the Brewerton and Frontenac burials of New York State (Brown 1904:325). This pattern likely indicates some form of cultural interaction and knowledge sharing over a very large geographic area. Indeed, similar artifact types have been found in Manitoba and Ontario (Steinbring 1966).

During the 1950s Dr. Robert E. Ritzenthaler of the Milwaukee Public Museum postulated that the origin of the Old Copper Complex "occurred when an early hunting and gathering group living in the Wisconsin area began to utilize native copper for the production of the distinctive utilitarian types of that area. At first, the nuggets in the glacial drift provided a handy source; later, copper was quarried from the trap rocks of Isle Royale and the Keweenaw Peninsula" along the south shore of Lake Superior in the Upper Peninsula of Michigan (Ritzenthaler 1957:323).

There has been little dispute over the last century that the primary copper sources that were exploited by the Old Copper Complex manufactures came from natural ore deposits spanning 120 miles along the southern shores of Lake Superior on the Keweenaw Peninsula. This native metal has an exceptional ratio of pure copper, typically over 95%. The most heavily utilized mines were discovered at Isle Royale, Keweenaw and Ontonagon. The following is an excerpt from the turn of the last century by Mr. J.T. Reeder of the Tamarack Mining Company in Calumet, Michigan, as he describes the ore deposits in this region.

"Around the Victoria location, the old Minnesota (now Michigan), the Rockland, the Mass and Adventure, and Winona, are hundreds of old Indian copper pits. To say that there are thousands would not be exaggerating. They extend from a few feet to as much as thirty feet into the gravel and solid rock" (Brown 1904:54).

Recent analysis of these prehistoric copper pits has generated great debate regarding the amount of copper extracted from them. Precisely what tonnage of copper was mined is difficult to determine, as no comprehensive study of the prehistoric mines has been completed. The largest estimate puts the total extracted copper ore during the Archaic period at as much as 1.5 billion pounds; a figure that has more to do with assumption than archaeological evidence  (Drier et. al. 1961). However, the real amount of native copper ore extracted during the prehistoric period is currently unknown (Martin 1995).

Float copper (left) was ground into chunks by glacial action and deposited in varying distances from its place of origin.  Hundreds of hammers (right) both grooved and ungrooved have been recovered from quarry pits in the Great Lakes areas.

There is less contention regarding the techniques used to extract the copper from the bedrock. Thousands of grooved hammerstones have been found in and around these prehistoric mining pits, supporting the theory that a great deal of manual labor was necessary to remove the copper ore. Another useful technique likely used to extract the ore was via thermal induced shattering, in which miners would light a fire beside the desired vein of ore, thus heating the rock surface. By applying water to this hot surface it would cause the rock to shatter, allowing for easier removal of the copper ore.

Copper was prepared for trade in three forms, bars that could range from 2 to more than 8 inches in length and were square in cross-section (upper left), shaped preforms (upper right), and finished tools (bottom).

Once the copper was extracted, the primary method of tool manufacture was by hammering the ore into the desired form. An additional fabrication technique was annealing, a process in which the ore was repeatedly heated to temperatures in access of 500 degrees, folded, and hammered into a more malleable state.  This process could be repeated as many as thirty times before being hammered into shapes as bars, shaped preforms, or finished products, all of which could be used for trade. Analysis of these artifacts exhibits obvious signs of layering, caused by hammering and folding the copper to produce the finished product. To date, there is no convincing evidence that archaic populations of the Old Copper Complex smelted copper to pour into pre-made molds (Martin 1999). Indeed, many copper artifacts show extreme uniformity and quality, indicating a high degree of technological specialization. This has led to speculation that Old Copper Complex artisans did in fact reach the level of smelting copper ore (Neiburger 1984). Exactly where these centers of innovation were located is so far poorly understood; yet the distribution of Old Copper finds across the landscape provides some indication of where the core Copper Complex areas were concentrated.

Old Copper Culture Artifacts

Tool types dating to 4000 B.C.

Scoops or gouges could be used for wood working.

Tool types dating to 2000 B.C.

Copper fish hooks must have been appreciated as an advanced tool by early cultures.  Knives took various forms including the "rat tail" appearance shown here.


This copper cache was recovered by Oliver Anttila while using his metal detector at a small secluded beach on Thunder Bay, Ontario, Canada. It was the sixth cache he had found on the bay and contained 122 pieces including a 6 5/8 inch awl, several conical and square socketed points, two crescent knives, and over 100 hammered copper nuggets prepared as preforms for future tools.

In an article by E.J. Neiburger, the reason for the long pointed tang on Old Copper Culture knives was explained. With the help of archaeologist Gary Weimer (drawing), Neiburger demonstrated how the tang was bent around the end of a solid-core handle material before bindings were applied.


Crescent knives usually had long extended handles or straps, but might also be simple crescents.  They would vary from ornamental crescents in that there were no holes for suspension.  Copper points were often socketed for hafting, but were also flat-stemmed.

Ornaments dating after 1500 B.C.

Copper gorgets of varying designs bracelets were ornamental in purpose and were a product of later copper usage that continued into the Mississippian and Historic periods.