Contributors-historians, anthropologists, and archaeologists-present numerous examples of the frontier as a shifting zone of innovation and recombination through which cultural materials from many sources have been unpredictably channeled and transformed. At the same time, they reveal recurring processes of frontier history that enable world-historical comparison: the emergence of the frontier in relation to a core area; the mutually structuring interactions between frontier and core; and the development of social exchange, merger, or conflict between previously separate populations brought together on the frontier.