In this article, I compare backstrap-loom weaving in three cultural contexts: the ancient Maya, the ancient Aztecs, and 20th-century Mesoamerica. Although continuities are present, important differences exist in the ways that weaving was situated historically. Among the Classic Maya, weaving defined class; in Aztec Mexico, weaving defined gender; and in 20th-century Mesoamerica, weaving defined ethnicity. A comparison of these cases suggests that historical study is a useful tool for both archaeologists and ethnographers. It promotes recognition of the diversity of practice and belief in ancient societies. It helps to define the scope of contemporary ethnographic study. It combats cultural essentialism and injects agency into our accounts. It enables us to acknowledge both the rich heritage of indigenous peoples and the fact of culture change. Comparative historical study provides a strong rationale for the continued association of archaeology and cultural anthropology as parts of a wider anthropological whole.