The package contains documentation of the spatial allocation factor development procedures for the 1980 National Acid Precipitation Assessment Program (NAPAP) area source emissions inventory, including the Fortran programs and input data files. The goal of the spatial allocation factor development effort was to create as many spatial surrogates as possible for each county to allow the user maximum flexibility in assigning county-level area source emissions to modeling grid cells. The surrogates are used to represent the subcounty distribution of area source emissions for each emissions category. Fourteen surrogate indicators were developed for use with the NAPAP inventory based on housing, population, and land use data. Once the subcounty distribution of each surrogate is determined, area source emissions categories are matched to the most appropriate surrogate indicators. The resultant Spatial Allocation Factor File is input to the Spatial Allocation Module of the Flexible Regional Emissions Data System.