Iowa's air monitoring data from 1959 to 1975 has been compiled in this report for the six major pollutants monitored in the State: suspended particulates, sulfur dioxide, nitrogen dioxide, carbon monoxide, hydrocarbons and photochemical oxidants. The data are presented in tabular form for each of the twelve Air Quality Control Regions in the State. To help the reader better understand the large amount of technical information in this report, additional sections discussing the pollutants and pollutant sources, the air monitoring network, and the analysis of data and trends have been added. Brief summaries of other Departmental projects, such as development of air basin modeling and investigation of pollution caused by leaf burning, are also included.