Accelerated mass spectrometry (AMS) and carbon isotope analyses provide strong tandem methodologies used by archaeologists to evaluate and reevaluate the histories of maize use in the Midwest. In this article, we present newly obtained AMS dates and carbon isotope assays of alleged maize samples from the Icehouse Bottom (40MR23) and Edwin Harness sites (22RO33). Based on original studies, samples were thought to date to the Middle Woodland period (ca. 300 BC–AD 400). The results show that samples either were not maize or date to post-AD 900. As of this finding, there are no longer any securely dated Middle Woodland macrobotanical remains of maize from the Eastern Woodlands of North America.

Late-glacial (17–11 cal ka BP) pollen records from midwestern North America show similar vegetation trends; however, poor dating resolution, wide-interval pollen counts, and variable sedimentation rates have prevented the direct correlation with the North Atlantic Event Stratigraphy as represented in the Greenland ice-core records, thus preventing the understanding of the teleconnections and mechanisms of late-Quaternary events in the Northern Hemisphere. The widespread occurrence of late-glacial vegetation and climates with no modern analogs also hinders late-glacial climate reconstructions. A high-resolution pollen record with a well-controlled age model from Crystal Lake in northeastern Illinois reveals vegetation and climate conditions during the late-glacial and early Holocene intervals. Late-glacial Crystal Lake pollen assemblages, dominated by Picea mariana and Fraxinus nigra with lesser amounts of Abies and Larix, suggest relatively wet climate despite fluctuations between colder and warmer temperatures. Vegetation changes at Crystal Lake are coeval with millennial-scale trends in the NGRIP ice-core record, but major shifts in vegetation at Crystal Lake lag the NGRIP record by 300–400 yr. This lag may be due to the proximity of the Laurentide ice sheet, the ice sheet's inherent slowness in response to rapid climate changes, and its effect on frontal boundary conditions and lake-effect temperatures.