By the time of his death in 1878, Joseph Henry was America's most eminent physical scientist. His achievements in the study of electricity, magnetism, and telegraphy during an era of national scientific aspiration had led to a thirty-year tenure as the first secretary of the Smithsonian, assuring his place in history as a key builder of an institutional framework for scientific inquiry. In this first biography of Henry since 1950, Albert E. Moyer reconstructs the crucial early phases of Henry's career, tracing how a boy of modest means in a nation of scant scientific resources attained international prominence in the field of physics. Moyer also offers a revisionist view of Henry's most enduring contribution - the discovery of mutual induction - and explains how the parallel work of British researcher Michael Faraday, who traditionally has been credited with the discovery, depended on a powerful electromagnet designed by Henry. Detailing Henry's progress from aspiring engineer leading a ragtag survey party in New York State's back country to adored Princeton professor teaching a generation not only the concepts but also the moral and religious implications of physics, the book concludes with Henry's candidacy in 1846 for the secretaryship of the fledgling Smithsonian Institution.