For more than thirty years, the History of Cartography Project has charted the course for scholarship on cartography, bringing together research from a variety of disciplines on the creation, dissemination, and use of maps. Volume 6, Cartography in the Twentieth Century, continues this tradition with a groundbreaking survey of the century just ended and a new full-color, encyclopedic format. The twentieth century is a pivotal period in map history. The transition from paper to digital formats led to previously unimaginable dynamic and interactive maps. Geographic information systems radically altered cartographic institutions and reduced the skill required to create maps.  Satellite positioning and mobile communications revolutionized wayfinding.  Mapping evolved as an important tool for coping with complexity, organizing knowledge, and influencing public opinion in all parts of the globe and at all levels of society. Volume 6 covers these changes comprehensively, while thoroughly demonstrating the far-reaching effects of maps on science, technology, and society--and vice versa.  The lavishly produced volume includes more than five hundred articles accompanied by more than a thousand images. Hundreds of expert contributors provide both original research, often based on their own participation in the developments they describe, and interpretations of larger trends in cartography. Designed for use by both scholars and the general public, this definitive volume is a reference work of first resort for all who study and love maps.