Historic emissions of sulfur oxides and nitrogen oxides were estimated for each state of the coterminous United States. The emissions were estimated by individual source category on the state level from 1900 to 1980 for every fifth year and for 1978. The source categories included power plants, industrial boilers, industrial processes, commercial and residential heaters, natural gas pipelines, highway vehicles, off-highway diesel engines, and all other anthropogenic sources. These emissions were calculated from salient statistics indicative of fuel consumption or industrial output, estimations of average statewide fuel properties, and estimations of emission factors specific to each source category over time. The emission estimates were then aggregated to show the emission trends by state, region, and all states combined. This paper summarizes the historic emission trends on a state, regional, and national scale. The trends are presented by source category and by major fuel type. The emission estimates allow temporal and regional trend comparisons between the emissions and chemical and biological effects trends derived in other studies. They provide a basis for assessing pollutant damage, for studying trends in stream chemistry and deposition monitoring data, and for evaluating proposed mitigation and control strategies.