Pure native copper nuggets are found throughout the upper Midwest in glacial till but they would have been very rare.  Natural nuggets were more frequently found found in Lake Superior deposits on Isle Royale and the Keweenaw Peninsula as ice sheets shrank at the end of the Ice Age.

Early copper artifacts in the upper Midwest are often thought to represent the Old Copper Culture of the late Archaic period. Utilitarian artifacts  such as projectile points, knives, crescents (perhaps ulus), awls, needles, pikes, spuds, celts, wedges, gouges, fishhooks, and spatulas are the most commonly known items. However,  bracelets and beads also were fashioned from the native copper. Native copper tends to be very pure and relatively soft.  Objects were made using the process known as cold hammering. There is no evidence that copper was smelted or cast at this early period.

Although the source of copper nuggets is remote and very limited, Old Copper Culture items have been found over a very wide area of the American Midwest. Their wide distribution suggests a broad trade network  that existed for centuries. Because of the unusual characteristics  and rarity of copper, it is very likely that copper objects had considerable spiritual power.