McGuire With National Science Foundation support, Dr. Randall McGuire and his colleagues will continue archaeological excavation at the site of Cerro de Trincheras. Located on a large isolated volcanic hill in northwest Sonora, Mexico, the site covers over a hectare and includes more than 870 terraces on the slopes of the hill. Some observable walls run for a hundred meters or more and approach heights of up to 3 meters. Previous work at the site indicates an occupation which extends from approximately 800-1450 AD. Excavation to date shows that terraces were used for cultivation. Domestic structures were also constructed on these surfaces. Building on a completed site map, Dr., McGuire and his team will excavate approximately 3-5% of the surface area. The excavation sample will be double-stratified by feature types and by loci defined in the mapping project. This procedure will allow for the estimation of parameters such as the number of houses per residential terrace and permit inferences about population and labor investment. The broadly based sample will provide chronometric dates for all portions of the site and allow reconstruction of synchronic activity structure across the site. The materials to be recovered - these include among other categories, ceramics, lithics, shell, bone and pollen - will be analyzed by a range of specialists. Cerro de Trincheras is a major and little known archaeological site which lies just South of the US border. The project will test a number of propositions about its prehistoric socio- political organization. At a lower level the research will address issues such as the timing of growth, the size and permanence of the human population, the nature of activities at the site and the role of the site in a larger regional and inter- regional economic system. At a higher level the work will address the nature of regional interaction in technologically simple prehistoric systems. It has been argued that major arhaeological cultu res in the US Southwest owe their existence to ties with central Mexico and that they can best be interpreted as parts of a much larger interaction network. An equally plausible interpretation sees the two as only weakly linked, essentially independent phenomena. Cerro de Trincheras because of its location between the two provides a means to examine these alternatives.