The National Historical GIS: Mapping the old and the brand new
By Jason Borah, GIS Analyst, Minnesota Population Center
Interested in mapping and analyzing census data from 1790 to 2010? Would you like to display the percentage of slave holding families per county along the Eastern Seaboard in 1790? How about mapping oat production in 19th and 20th century Minnesota? Perhaps you are more interested in recent census data, like analyzing the change in number of vacant housing units between 1980 and 2000 in the cities and towns within 50 miles of major metropolitan areas across the United States.
The spreadsheet data and historical GIS shapefiles needed to address these topics and hundreds more are all available absolutely free through www.nhgis.org
, an ongoing project of the Minnesota Population Center
(MPC) at the University of Minnesota.
Site Updates include 2010 Data
While many MN GIS/LIS Consortium members are familiar with the NHGIS website, launched in 2005, recent updates have added a modern look, improved search capabilities, detailed help documentation, and significantly more data! The latest data release, 2010 Census Summary File 1, helps keep NHGIS relevant to modern data users. With the latest data additions, NHGIS now serves up over 420 historically accurate shapefiles with approximately 28 million polygon records and nearly 11,000 tabular data tables spanning 23 decades and all corners of the country .
Streamlining Use of Census Data in GIS
But why use NHGIS instead of the US Census website for accessing census data? Many GIS users are unaware that the US Census Bureau only provides decennial census data from the 1990, 2000 and 2010 censuses in formats helpful to GIS users through TIGER and American FactFinder. Older data are typically available from the US Census Bureau as PDF copies of scanned census reports – usable when hand entering a small amount of data but daunting in most circumstances.
Beyond simply providing the data, NHGIS does so with the geospatial professional in mind. Data for multiple years, geographic levels and topics can be quickly downloaded together in one time-saving extract that also reduces the number of files to track. In addition, users’ data extracts are stored indefinitely, providing fast and hassle-free extract revisions and resubmissions. Working with the data is also streamlined; a unique GISJOIN text field seamlessly joins tabular data to shapefiles, while attribute names follow GIS naming conventions regarding length, special characters and duplicates.
More Data and Time-Series on the Way
The NHGIS project began in 2001 with an ambitious $5 million National Science Foundation (NSF) grant to gather all surviving census data from 1790 – 2000, format them consistently, develop comprehensive standardized machine-readable documentation, create high-precision electronic boundary files and develop a web-based tool for disseminating the data. NHGIS, with continued funding through NSF and the National Institutes of Health, is now working hard to release additional 2010 Census and American Community Survey data, as well as other non-census data. NHGIS is also in the early stages of adding a major temporal component to its data holdings. This addition will provide time-series tables that link comparable variables across multiple (varying from 2 to 23) censuses as well as providing geographic boundary files for “minimally aggregated” geographic levels that will allow for easier research involving fixed locations through time.
In addition, NHGIS, as part of the MPC, will be exhibiting at a number of national conferences, including the Association of American Geographers (AAG
) meeting in New York City and the American Planning Association (APA
) Conference in Los Angeles. If you will be attending, please stop by, say hello and ask a question or two. For our complete conference schedule, please visit our website