Book excerpt: Traditional Arid Lands Agriculture is the first of its kind. Each chapter considers four questions: what we don’t know about specific aspects of traditional agriculture, why we need to know more, how we can know more, and what research questions can be pursued to know more. What is known is presented to provide context for what is unknown. Traditional agriculture, nonindustrial plant cultivation for human use, is practiced worldwide by millions of smallholder farmers in arid lands. Advancing an understanding of traditional agriculture can improve its practice and contribute to understanding the past. Traditional agriculture has been practiced in the U.S. Southwest and northwest Mexico for at least four thousand years and intensely studied for at least one hundred years. What is not known or well-understood about traditional arid lands agriculture in this region has broad application for research, policy, and agricultural practices in arid lands worldwide. The authors represent the disciplines of archaeology, anthropology, agronomy, art, botany, geomorphology, paleoclimatology, and pedology. This multidisciplinary book will engage students, practitioners, scholars, and any interested in understanding and advancing traditional agriculture.