Science, medicine, and technology have become increasingly important to the average individual in modern society. The importance of these three fields is in many ways one of the defining characteristics of modernity. Understanding their history is essential for educated individuals. Science,medicine, and technology are not static endeavors but processes, bodies of knowledge, tools, and techniques that are constantly growing and changing. The entries in this encyclopedia explore the changing character of science, medicine, and technology in the United States; the key individuals,institutions, and organizations responsible for major developments; and the concepts, practices, and processes underlying these changes. Especially since the early decades of the twentieth century, American science, medicine, and technology have played dominant roles internationally. Entries explore distinctive characteristics of American institutions and culture that help explain this development. At the same time, the encyclopedia situates specific events, theories, practices, and institutions in their proper historical context and explores their impact on American society andculture. Entries are written by the experts in the field. Students not only from the humanities and social sciences but also from the sciences and the medical sciences should be attracted to the broad-ranging and in-depth analysis in the encyclopedia.