The Large Power Plant Effluent Study (LAPPES) was initiated in Western Pennsylvania to evaluate the extent and effects of air pollution resulting from the largest complex of coal-burning generating stations in the United States. During 1968 four series of field experiments were conducted in an area surrounding the Keystone Generating Station; these experiments consisted of ground-based and air-borne plume measurements supported by extensive meteorological observations. Part 1 describes the topography and climatology of the generating station complex, the sulfur dioxide and meteorological monitoring equipment, and experiment operating procedures. Part 2 presents tabulations of plant operational parameters and air quality and meteorological data collected during 1968. Analyses of the data, evaluation of existing plume rise and dispersion theories, or development of new diffusion models are not presented here. (Author)