The Shaw Butte Hilltop Site: A Prehistoric Hohokam Observatory

The Sonoran Desert of Southern Arizona was once occupied by the prehistoric Hohokam, a group of agriculturalists who constructed thousands of kilometers of irrigation canals as well as public architecture, including platform mounds and bailcourts. They also appear to have been keen astronomical observers, although the subject of Hohokam archaeoastronomy remains underexplored. This paper summarizes previous Hohokam archaeoastronomy studies, discusses O'odham (Piman) Indian calendar systems, outlines a theoretical framework for studying Hohokam archaeoastronomy, and present the results of a study of a fortified hill site in the Phoenix Mountains, Arizona. This site appears to have served as an observatory, where the Hohokam marked the appearance of solstices and equinoxes with light patterns in an artificially constructed rockshelter, and by the location on the horizon of sunrise and sunset in relation to architectural features. Furthermore, some of the petroglyphs at the site which may be associated with astronomical observations are described. The implications of a Hohokam calendar system also are discussed.