in archaeological investigation such as the study of pre-Hispanic cities in their totality as complex integrated cultural systems instead of limiting investigation to the monumental ceremonial centers or other sectors of a city, as if they were isolated from the rest of settlement. Another contribution was the perspective of settlement pattern studies that transcended the concept of isolated sites and organized archaeological investigation in terms of regional settlement systems or other groups of sites forming larger analysis units. New investigations inspired by these projects modified and expanded the kinds of problems and information being studied, recovered more data about many specific cultural processes, and provided a more integrated vision of pre-Hispanic societies.

During the following decades, settlement-pattern studies became common in Mexico, and some of the first projects of this type were salvage archaeology programs undertaken by the National Institute of Anthropology and History. Fieldwork and excavation were coordinated with the construction of hydroelectric dams and modern irrigation systems, such as (during the 1960s and 1970s) the projects of Infiernillo, Palos Altos, and La Villita in Guerrero; La Angostura, Mal Paso, Chicoasen, and Itzantun in Chiapas; Chicayan in Veracruz; and Pujalcoy in San Luis Potosí. More recently, a number of salvage settlement pattern and excavation programs have been carried out in conjunction with the construction of natural gas lines. The quantity of salvage investigation has increased greatly since 1970, and it now forms an integral part of Mexican government archaeology. One of the most extensive accumulations of salvage data came from nearly twenty-five years of excavation during the installation of Mexico City’s subway system.

Some of the major nonsalvage regional studies include projects in the Puebla-Tlaxcala, the Valley of Oaxaca, the Komchen (Yucatán), the Coba (Quintana Roo), the Rio Bec and the Tula area. There were also French and Mexican surveys in the Huasteca (Ochoa 1979).

Two key regional projects investigating the origins of Mesoamerican civilization among the Gulf coast Olmec were centered at San Lorenzo Tenochtitlán in Veracruz (Coe and Diehl 1980) and La Venta in the state of Tabasco (González Lauck 1988). The San Lorenzo project included ecological and agricultural studies that provided crucial data concerning Olmec subsistence, and the La Venta project made settlement pattern studies of sites that were over 3,500 years old.

In the field of what Latin Americans call “prehistoric archaeology,” the study of very early human occupations of the late Pleistocene and later preceramic times, there have been important changes. Multidisciplinary projects investigating long sequences of occupations for specific regions, in conjunction with detailed reconstructions of paleoclimates and paleoenvironments, are now the norm. In the southern basin of Mexico, a major program at the site of Tlapacoya by the Department of Prehistory (Lorenzo and Mirambell 1986; Niederberger 1976) uncovered one of the earliest sites in the Americas, over 20,000 years of human occupations. A probable long occupation by early hunters was investigated by Irwin-Williams (1978) at Valsequillo in Puebla. A multidisciplinary project concerning the origins of agriculture and settled life was directed by Kent Flannery (1986) in the Valley of Oaxaca.

As part of the growing interest in studying social and economic processes, new techniques and theoretical goals have been developed for the analysis of archaeological materials, especially ceramics and lithics. Ceramics are no longer studied exclusively to establish chronologies and occupation sequences but also to identify artifact functions, activity areas, and technological processes. Numerous programs investigate ceramic production (workshop) and trade systems with the aid of petrographic and trace element analyses (Rice 1986).

Lithic artifacts and tools were only briefly described in Mesoamerican reports before the 1960s, but Lithic Analysis has improved greatly and now the technological production sequences and specific functions of tools are investigated. Use/wear functional studies are common, and there is considerable research concerning lithic workshops, mining, and trade systems (Gaxiola and Clark 1989).

Historical archaeology, investigating cultures