Kidder then embarked on a series of expeditions to the Southwest, many in northeastern
Arizona. These expeditions were sponsored by Harvard's
Peabody Museum of Archaeology and Ethnology and the associated
Robert S. Peabody Museum of Archaeology at
Phillips Academy in
Andover, Massachusetts. From 1915 to 1929, Kidder conducted site excavations at an abandoned pueblo near
Pecos, New Mexico, now the
Pecos National Historical Park. He excavated levels of human occupation at the pueblo going back more than 2000 years, and gathered a detailed record of cultural artifacts, including a large collection of
pottery fragments and human remains. From these items, he was able to establish a continuous record of pottery styles from 2000 years ago to the mid-to-late 19th century. Kidder then analyzed trends and changes in pottery styles in association with changes in the Pecos people's culture and established a basic chronology for the Southwest. With
Samuel J. Guernsey, he established the validity of a chronological approach to cultural periods. Kidder asserted that deductions about the development of human culture could be obtained through a systematic examination of stratigraphy and chronology in archaeological sites. This research laid the foundation for modern archaeological field methods, shifting the emphasis from a "gentlemanly adventure" adding items such as whole pots and cliff dwellings to museum coffers to the study of potsherds and other artifacts in relation to the cultural history. Pioneering archaeologists in other regions of the United States completed the transformation of professional methodology initiated by Kidder. His
Introduction to the Study of Southwestern Archaeology, published in 1924, was the first synthesis of North American prehistory based on professionally recovered empirical data. In spite of his efforts at documentation, Kidder's conclusions have sometimes been criticized for a lack of integration between his field reports and his later synthesis and interpretation of that data. However, Kidder clearly emphasized archaeology's need for a scientific "eye" in the development of fact collecting techniques and clear definitions. In the late 1920s, Kidder started the
Pecos Conferences for archaeologists and ethnologists working in the American southwest. In 1927, a temporal system of
nomenclature, known as the
Pecos Classification System, was established for use in southwestern sites. Archaeologists have since used the sequence, with later variations, to assign approximate dates to dozens of sites throughout the Southwest and to determine cultural ties and differences among them. The same year he was elected a Fellow of the
American Academy of Arts and Sciences. He was elected to the
American Philosophical Society in 1934. In 1936, Kidder was elected to the United States
National Academy of Sciences in 1936. That same year, he formally used the Navajo term "
Anasazi" to define a specific cultural group of people living in the southwest between approximately 200 BC and 1300 AD. This term had been casually used by excavators for many of the "ancient people" since the early explorations of
Richard Wetherill, and had been informally used in the work of the Pecos Conferences. As an associate in charge of archaeological investigations (1927–1929) and as chairman of the division of historical research (1929–1950) at the
Carnegie Institution, Kidder conducted a broad-scale multidisciplinary research program in
Kaminaljuyu in the
Guatemalan highlands which established the framework of
Maya stratigraphy. In 1939 he became honorary curator of Southwestern American archaeology at the Peabody Museum, Harvard. In 1951, Kidder, in discussions with
Thomas Stuart Ferguson and
Gordon Willey of Harvard University, was instrumental in establishing a foundation dealing with the status of archaeology in
Mexico and
Central America. In regard to those discussions, Ferguson wrote that the three scholars agreed
“...it was unfortunate that so little work was being carried on in so important an area and that something should be done to increase explorations and excavations....Despite the amazing discoveries made between 1930 and 1950, work on the Pre-Classic was virtually at a standstill in 1951. The result of the discussion was that we agreed to set up a new organization to be devoted to the Pre-Classic civilizations of Mexico and Central America—the earliest known high cultures of the New World.” The following year, the
New World Archaeological Foundation (NWAF) was incorporated in California, as a nonprofit, scientific, fact-finding body. ==Native American Graves Protection and Repatriation==