Users who must combine demographic, economic or other data in a geographic context are often hampered by the integration of tabular and map representations. Static, paper-based solutions limit the amount of data that can be placed on a single map or table. By providing an effective user interface, we believe that researchers, journalists, teachers, and students can explore complex data sets more rapidly and effectively. This paper presents Dynamaps, a generalized map-based information-visualization tool for dynamic queries and brushing on choropleth maps. Users can use color coding to show a variable on each US state or county, and then filter out areas that do not meet the desired criteria. In addition, a scattergram view and a details-on-demand window support overviews and specific fact finding.