Two accelerator mass spectrometry (AMS) dates obtained from samples of Zea mays from the Holding site, 11MS118, in the American Bottom near East St. Louis, Illinois, establish the presence of maize in the Mississippi Valley between 170 B.C. and A.D. 60. The dates finally establish the occurrence of Middle Woodland maize in Illinois and are the earliest dates thus far for maize east of the Mississippi River. Other reports of early Middle Woodland maize in the Midcontinent region should not be discounted unless AMS dating and other supporting information show the maize to be a contaminant at the site at which it occurs. Recent stable carbon-isotope experiments suggest that the relative contribution of maize to Middle Woodland diets is still an open question.