Since December 1983, the U.S. Geological Survey (USGS) and the U.S. Bureau of the Census (Census Bureau) have been cooperating to establish a 1:100,000-scale transportation and hydrography digital data base by June 1987. The magnitude of the task of converting to digital data the transportation and hydrography information contained on 1,823 1:100,000-scale quadrangles and the short timeframe for accomplishing this project required the development and implementation of state-of-the-art digital production systems in both agencies. The recently completed 1:100,000-scale digital data files are now part of the National Digital Cartographic Data Base (NDCDB) maintained by the USGS. The USGS has begun distribution of these files as U.S. GeoData 1:100,000-scale Digital Line Graphs (DLG's). The transportation and hydrography data are being distributed in 30- by 30-minute blocks each composed of 16, 7.5-minute files. These 30- by 30-minute areas correspond to the east or west halves of the 1:100,000-scale maps. There are presently 1,694 east and 1,685 west halves in the 95-percent-complete data base. These data are topologically structured, attribute coded and available in standard and optional DLG format. Because 1:100,000-scale DLG's have a topologically structured format in which relationships among features are encoded, the data can be used for general spatial applications, to perform statistical calculations, or for tabulations. The Census Bureau is using the 1:100,000-scale transportation and hydrography digital data as the cartographic base for their Topologically Integrated Geographic Encoding and Referencing (TIGER) System, which covers the Nation, Puerto Rico, Virgin Islands, and outlying areas of the Pacific. The Census Bureau is adding information such as feature names and political and Census statistical boundaries and codes to the TIGER files for use in the 1990 decennial and subsequent economic censuses and surveys. For the 1990 decennial census alone, the Census Bureau will produce over 300,000 individual maps from these data for enumerator use. The joint venture between the USGS and the Census Bureau has great economic significance. The 1:100,000-scale digital cartographic data combines the qualities of sufficient detail, adequate content, and nationwide coverage that will allow and encourage increased use of spatial analysis methods. For example, after 1990, the data reported by the Census Bureau from the 1990 decennial census can be related to features included in the 1:100,000-scale data base. The USGS and the Census Bureau will be making all of these data available through both agencies' information outlets. Discussions are now underway to establish procedures and mechanisms for selling each other's data and for joint marketing of products. This compatibility of census data with the USGS digital cartographic data base can only be of increased benefit to all Federal, State, local, and private users.