From 2001 through 2007, researchers at the University of Minnesota and other institutions have been assembling the National Historic Geographic Information System (NCGIS). The NHGIS was designed to make the rich body of aggregate census data accessible within a GIS framework. Project goals were to gather all surviving census data from 1790 to 2000, format them consistently, develop comprehensive standardized machine-readable documentation for those data, create high-precision historical electronic boundary files describing census tracts and counties, and develop innovative web-based tools for disseminating statistical data, geographic data, and metadata. As the project's original goals were attained, however, new opportunities had presented themselves. This renewal award will support continued work to update and improve the NHGIS by upgrade the NHGIS system in response to new geographic standards and statistical infrastructure that have become available during the last five years. In particular, the project will realign NHGIS boundary files to ensure compatibility with new standards. Because the Census Bureau is substantially revising its TIGER/Line files to improve accuracy, NHGIS files will be realigned so that the historical data will be synchronized with new GIS data releases. NHGIS managers also will add geographic levels to NHGIS files for 1980 through 2000 to ensure that these data remain available to researchers. The new NHGIS geographies will include block, place, enumeration district, congressional district, and Zip Code Tabulation Areas. NHGIS managers also will incorporate the American Community Survey (ACS) into NHGIS. In order to take advantage of the continuous data-collection possibilities offered by the ACS but also data are collected continuously instead of on a specified census day and the reference period for aggregate statistics varies according to the population size of the geographic unit, incorporating these data into NHGIS will require development of innovative metadata and software. New activities also will provide user support and dissemination, and the new maps and data will be added to the NHGIS online mapping application, Social Explorer.
Continued refinement of the NHGIS will permit this resource to accelerate the process of democratizing access to the census. The database is being used widely for social science training, by the media, for policy research at the state and local levels, and by the private sector. The NHGIS database will be increasingly accessible for basic social science research, broadening the scope of local and regional analyses to explore variations across time and space simultaneously.
