| Remnant raised fields, elevated planting surfaces that improve cultivating conditions, are common in the Upper Midwest. Prehistorians suggest that native peoples built them to ameliorate microclimates in cool environments.; Cartographic documents, archaeology, historic records, and ethnography indicate that areas in Canada around Lake Winnipegosis, the Mackinac Straits, the central Ottawa River valley, Lorette, and the Bay of Fundy defined the northern margins of agriculture during the Little Ice Age (1450–1850 AD). Plain fields and corn hills existed in all of the above areas. Native strategies for farming the northern margins included site selection, cultivar diversity, and specialized crop-tending practices, but not, except for Mackinac, ridged field agriculture.; Analyses of 461 raised field sites in Wisconsin show that native peoples farmed varied environments, from wetlands to uplands, prairies to forests, across diverse soil landscapes, and in locales with 90 to 170 consecutive frost-free days. Most raised fields here occur on Class I agricultural lands with a minimum growing season of 150 frost-free days. Wetland fields, however, represent native land reclamation. Experiments demonstrate that most Wisconsin raised fields are too small to drain radiation frosts.; Archaeological excavation, soil analyses, and micromorphology show that ridged fields improve cultivating conditions in multiple ways. Effigy Mound peoples built the Hulburt Creek ridged fields in central Wisconsin around 1000 AD. They ditched a prepared surface and built planting surfaces from excavated deposits. The Hulburt Creek fields improved soil fertility. Planting surfaces drained water during wet years while ditches stored water during dry ones. Mill Creek peoples broke prairie sods at the Litka site in northwestern Iowa around 1100 AD. They mounded soil into ridges to slow erosion and provide water storage. Native peoples often built raised fields incrementally, annually adding soil to buttress maize roots, maintain soil fertility, and retard weeds, pests, and diseases.; Varied field types across the northern margins, myriad ecological settings for Wisconsin raised fields, and site-specific investigations argue against climatic explanations for raised field distributions. Some native fields could be measured in square kilometers, even at the margins. Native North Americans were skilled agriculturalists who cultivated large fields in many environments. |
