Ag Atlas Maps
http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Ag_Atlas_Maps/

Geographic information system (GIS) and desktop publishing technologies were used in the production of maps for this atlas. NASS developed an automated map production system to generate digital map files based on statistical data from the 2007 and 2002 Censuses of Agriculture. The system utilized agricultural statistical data files, geographic area boundary files, land use/cover boundary files, map parameter data files, and customized GIS and statistical software to produce thematic choropleth and dot-density maps. The customized software performed statistical calculations to class the data into categories and to allocate the number of dots for a geographic area. The software also executed other cartographic functions including, assigning symbology to represent the data; randomly placing dots; creating and positioning map titles, legends and notes; and outputting individual maps to digital image files. Colors for the maps were selected with the assistance of ColorBrewer, an online tool for selecting map color schemes. The color schemes were developed by Dr. Cynthia A. Brewer at Pennsylvania State University. The U.S. Census Bureau provided a generalized county boundary file, urbanized areas boundary file, land use/cover boundary file (originator – USGS), and county-level land area/perimeter data file. NASS modified the county boundary file to show the county-level geographic areas for which agriculture census statistics are reported. The statistical data and geographic areas were identified by Federal Information Processing Standards (FIPS) codes that allowed for a 1-to-1 correspondence between the data and the geographic area. NASS updated the land use/cover boundary file with generalized urbanized areas. The continental U.S. and Hawaii were mapped at a scale of 1:21,000,000 and Alaska used a map scale of 1:63,000,000. The maps were projected using Albers Equal Area Conic projection. This has been added to Agriculture Resources Subject Tracer™ Information Blog.