Usulutan pottery is a major characteristic of Preclassic ceramic assemblages in southern Mesoamerica. This distinctive "resist" decorated pottery has long been considered a significant marker of southeastern influence in other areas of Mesoamerica and has been an important element in discussions of external stimuli on the development of Maya civilization. The origin, evolution, and technology of Usulutan have been debated for over 50 years. New archaeological evidence from western El Salvador now provides solutions to several aspects of this debate. The discovery of a complete, well dated sequence of resist and Usulutan decorated ceramic types demostrates a western Salvadoran origin and development for this pottery, tracing the tradition back to the Early preclassic period. This sequence provides a spatial and temporal framework for future studies of Usulutan techology. The new evidence also requires a reasssessment of the nature and significance of the Late Preclassic spread of Usulutan pottery in southern Mesoamerica.