in 1966 testing the basic validity of the frontier concept, although he noted that “the means for testing the proposition were not defined. Sharer’s summary statement on the Chalchuapa project is a processual model of frontier dynamics beginning with the presence of an Olmec enclave from the Gulf of Mexico and ending with the invasions of the Pipil and Pokomam peoples in the postclassic period. In 1986, Arthur Demarest could open his report of work at Santa Leticia with the statement that Salvadoran archaeology has always been approached either explicitly or implicitly as the study of a frontier area. In practice, this meant that interpretive statements about the country’s archaeology were concerned with the timing and nature of external contacts, preferably with Mesoamerican sites.

Demarest’s own work exemplifies the way that this culture-historical concern has continued to pervade newer problem-oriented studies that followed the successful definition of anchoring sequences in eastern and western El Salvador by the Quelepa and Chalchuapa projects. Demarest identified four issues addressed in his research at the small western Salvadoran site of Santa Leticia: the location of the Mayan frontier; the origin and techniques of manufacture of Usulutan ceramics; late preclassic ceramic connections, invasions, and migrations; and the question of Olmec affinities for local stone sculptures labeled “potbellies.” All four issues involved the degree and nature of contact between Salvadoran and Mesoamerican peoples. Demarest’s project applied physical and chemical analyses to Usulutan ceramics to address the nature of the technology and reinforce the interpretation of stylistic similarities in ceramics. He also employed radiocarbon dating to help choose among various scenarios for connections between local stone carving traditions and those of Mesoamerica. But these and other innovations in methods were only applied to traditional concerns of linguistic or ethnic identity.

While Demarest sought to clarify the nature of preclassic relationships of Salvadoran archaeological sites with Mesoamerica, other contemporary researchers addressed the opposite extreme of the chronological sequence, the presumed intrusion of Mexican Pipil in the postclassic period. The presence of Nahua-speaking peoples in the country led early researchers to search for Mexican traits that would be diagnostic of the movement of these peoples from their presumed homeland. Haberland’s definition of Marihua Red-on-Buff and comparison with Mexican ceramic types filled the requirement for a distinctive Pipil pottery style. Andrews, noting the presence in private collections from around Quelepa of wheeled figurines and the recovery from the site of ball-game sculptures, both better known from Veracruz, mexico, looked to that region for analogues to Quelepa’s distinctive late-classic pottery styles. Later archaeology at the site of Cihuatan formalized the definition of a Pipil archaeological assemblage, drawing further comparisons with Veracruz and tracing the migration of Nahua speakers from Mexico to Nicaragua (Bruhns 1980; Fowler 1989; Kelley 1988). These migrations were viewed as culture-historical events, consequences of the collapse of the cities teotihuacán or Tula in central Mexico.

The underlying assumption that the prehistory of El Salvador was marked by abrupt disjunctions had its origin in the volcanic stratigraphy first reported in the 1920s. The exploration of this phenomenon inspired the first systematic regional program of survey and test excavations in the country. As a member of the Chalchuapa project, Payson Sheets in 1970 collaborated with geologists on the identification of the source and dating of a layer of volcanic ash found at the site, and in 1975, he pursued the identification of the extent of the effects of this eruption. Between 1978 and 1980, Sheets directed a regional project in the Zapotitan Valley (including Campana San Andres) with an explicit processual concern with past human response to natural hazards and their effect on the local cultural ecology. He documented a series of volcanic eruptions that affected the region with varying intensity of impact on the local population. By assessing technological style, he was able to argue that resettlement of the area after the most extreme disaster came from neighboring Maya regions.

Sheets promoted the use of a wide range of specialized analyses to explore the environment