Findings from a new archaeological survey challenge long-held assumptions that intensive agriculture in North America was limited to centralized societies or favorable environments. The findings reveal an extensive precolonial agricultural landscape in Michigan's Upper Peninsula, suggesting Indigenous American communities cultivated maize intensively between 1000 and 1600 CE, despite a cold climate and marginal growing conditions. Indigenous American communities across what is now the United States increasingly relied on intensive maize cultivation, an agricultural shift that accompanied profound social and environmental transformations. Yet in marginal regions like northern Michigan – characterized by dense forests, a cold climate, and a short growing season – the scale of maize cultivation and the level of agricultural intensification remains uncertain, especially given the abundance of wild rice. Direct evidence of precolonial intensive agriculture across much of the eastern United States is exceedingly rare because most indigenous agricultural landscapes have been irreversibly altered by colonial European and American plowing, settlement, and industrial activities. However, the Sixty Islands archaeological site in Michigan's Upper Peninsula preserves rare evidence of complex precolonial raised, ridged agricultural fields and maize cultivation. According to the authors, the Sixty Islands site stands as the only known preserved precolonial field site in Michigan, though it is currently under threat from proposed mining activities.
To better understand the scope and nature of these ancestral agricultural practices, Madeleine McLeester and colleagues conducted drone-based lidar surveys and excavations at the Sixty Islands site. The findings reveal a remarkably well-preserved and expansive system of raised garden beds spanning over 300 hectares, representing the most extensive known example of ancestral Native American agriculture in the eastern United States. Radiocarbon dates indicate that the ridged fields were actively used between 1000 and 1600 CE, overlapping with the Little Ice Age – a period marked by cooler temperatures. Despite the harsh climate, limited labor pools, and the presence of wild alternative food staples, ancestral farmers cultivated maize and other crops with notable success. Moreover, McLeester et al. uncovered evidence of advanced soil management, including the incorporation of composted domestic refuse and nutrient-rich wetland soils to enhance fertility. In addition to agricultural structures, the survey also revealed a host of associated archaeological features, including burial mounds, ceremonial earthworks, and habitation sites, suggesting that farming was well integrated into the broader cultural landscape. Contrary to long-standing assumptions that intensive agriculture is tied to centralized political power and large populations, the authors show that this complex system was created by small-scale, egalitarian communities.
