Drainage areas were determined for more than 7,000 sites in Wisconsin's 11 major river basins, including all named streams draining 5 or more square miles, and all unnamed streams draining 10 or more square miles. Also determined are drainage areas for gaging stations, sewage-treatment plants, dams, major highway crossings, and other sites where discharge measurements or water-quality data are available. Drainage areas were delineated on U.S. Geological Survey topographic maps. Drainage areas are shown in tabular form under six headings: station number; stream name, rank, and location; township, range, and section; county; type of site; and drainage area. Eleven major-river-basin maps show the location and station number of key sites.