Between 1800 and 1870 meteorology emerged as both a legitimate science and a government service in America. Challenging the widely held assumption that meteorologists were mere data-gatherers and that U.S. scientists were inferior to their European counterparts, James Rodger Fleming shows how the 1840s debate over the nature and causes of storms led to a meteorological crusade that would transform both theory and practice. Centrally located administrators organized hundreds of widely dispersed volunteer and military observers into systematic projects that covered the entire nation. Theorists then used these systems to observe weather patterns over large areas, making possible for the first time the compilation of accurate weather charts and maps. When in 1870 Congress created a federal storm-warning service under the U.S. Army Signal Office, the era of amateur scientists, volunteer observers, and adhoc organizations came to an end. But the gains had been significant, including advances in natural history and medical geography, and in understanding the general circulation of the earth's atmosphere.