Five accelerator mass spectrometer (AMS) dates on corn (maize or Zea mays) from the Grand Banks site, Ontario, range from cal A.D. 540 to 1030. These are the earliest directly dated corn samples in the Lower Great Lakes region. The presence of corn during the Princess Point Complex, a transitional Late Woodland phase preceding the Ontario Iroquoian Tradition, is confirmed as is an early presence of the Princess Point culture in Ontario. Maize appears to have spread rapidly from the Southeast and/or Midwest to Ontario. The corn cupules and kernel remains are fragmentary, as they are elsewhere in the Eastern Woodlands during this period. The limited morphological data indicate that the corn is a diminutive form of Eastern Eight-Row, or Eastern Complex, maize.