Most of the chapters in this volume were originally presented as contributions to a symposium organized by Little and Kennedy at the American Association of Physical Anthropologists (AAPA) annual meeting in Milwaukee, Wisconsin, in 2005. This was an anniversary symposium marking the 75th year of the AAPA, and three of the contributors to this volume (Loring Brace, Matt Cartmill, and Eugene Giles) also contributed to the 50th anniversary volume in 1980 that was edited by Frank Spencer. Two of the chapters here were added to the collection after the symposium: an introduction to the collection by the editors and a biographical overview of the contributions to physical anthropology made by the founder of American anthropology, Franz Boas. The thirteen chapters that constitute the volume do not present a comprehensive history of physical anthropology in the United States during the 20th century. Rather, they highlight numerous aspects of histories of this science as it developed to maturity during this period. The 20th century began in the United States with only a handful of physical anthropologists continuing antiquated 19th-century practices, and ended with 2,000 professional physical anthropologists throughout the nation participating in modern scientific inquiry. Other major sources of historical and biographical documentation for physical anthropology are reviewed in Chapter 1. We acknowledge, with our thanks, the assistance of the organizers of the 2005 AAPA meeting and the editors of Lexington Books, particularly Alyc Helms, Jana Wilson, Melissa Wilks, and Patricia Stevenson, who guided this book through the production process. We also thank Adrienne V. Little, who provided valuable assistance with proofreading.