About the Data


Column Headings

Free Data Downloads


The data on this web site are available in several commonly-used formats: 

  • As dynamic web-based maps. A web browser that supports Dynamic HTML, JavaScript, and Silverlight is required. Version 7 or higher of Internet Explorer® or Mozilla Firefox® supports this capability. Because of inconsistencies between their implementation of Dynamic HTML, this site has been optimized for Internet Explorer. Maps are organized by district types: state house, state senate and U.S. congress. They should be viewed with a computer screen set to at least 800x600 resolution and 65,000 colors.
  • As Microsoft Excel® spreadsheets with an .xls file extension.
  • As ZIP files, which need to be unzipped into their original formats before they become accessible by software such as word processors, GIS software, databases or spreadsheets. Zip files are files that have been compressed for faster download. 

    For example, congressional district boundaries and data may be available in the following zipped shapefile: C0926shp.zip. The "shp" string in the name arbitrarily denotes a shapefile while the ".zip" extension indicates that this shapefile was compressed for faster web download. To use this file with a GIS system such as ArcView, the file must first be unzipped. Unzipping it will create a set of new files on disk, which can be read by the GIS. There are a number of unzipping utilities available. The most popular of them is WinZip. A free trial version of WinZip can be downloaded from here.