The tandem accelerator mass spectrometer provided critical dating of corn remains in Archaic levels of juxtaposed Archaic and Hohokan occupations on Tumamoc Hill in Tucson, Arizona. This new radiometric technology confirmed an Archaic placement suggested by stratigraphy and artifact distributions. The small sample of intact remains resembles other directly-dated early corn in the Southwest and reinforces an interpretation of preceramic cultivators in the Sonoran Desert.