A program of surveys and test excavations has located 53 prehistoric open midden sites in the Bahamas and procured a large artifact sample from them. Sites in the central Bahamas, concentrated in the eastern islands of the area, are characterized by the shell-tempered Palmetto Series pottery. While sharing specific modes with Antillean cultures, it is an indigenous development, originating in the Caicos where the earliest sites have only ceramics imported from the Antilles. Distribution of sites and ceramic analyses suggest a movement of Antillean Arawaks to the Caicos to secure salt. An indigenous cultural tradition developed there by shortly after 1000 A.D. and spread rapidly to the central Bahamas. Factors affecting the limits of cultural expansion were the temperature and rainfall requirements of bitter manioc agriculture, which eliminated the northern Bahamas, and perhaps, in part, a time factor affecting expansion to the west.