A review of the history of marine-shell chemical-sourcing efforts preceeds the introduction of this project. Atomic-absorption spectroscopy (AAS) was used to assay levels of Ca, Mg, Fe, and Sr, in 44 prehistoric Busycon carica and Busycon perversum specimens from the eastern United States. Control shells (35) were collected from food refuse in coastal archaeological sites from Long Island to the Mexico—United States border. Subject shells came from nine Archaic and Mississippian sites. Elemental ratios were clustered to derive a probable water-body origin for the nine artifacts. The influence of diagenesis, body part, and species was negligible, but geography heavily influenced the results. The three shells from Monks Mound indicated origin in tropical, eastern Gulf, and Atlantic water. The shells from the Indian Knoll, Mulberry, and Tatham sites appear to have originated in eastern Gulf waters. The shell from the Archaic-period Ward site seems to have come from tropical water.