Where to Find Elusive GIS-Ready Census Data

Begun in 2001 as a project of the Minnesota Population Center, a unit of the
University of Minnesota, with funding from the National Science
Foundation, NHGIS was created with "an ambitious goal to collect, format, and freely disseminate all
available aggregate census information for the entire country from the
past 220 years," write Jason Borah and Jonathan Schroeder. With an "ever-expanding cache of 15,000 tables and 430 shapefiles," NHGIS admirably fills in the gaps in data available through the U.S. Census Bureau's American FactFinder.

One of the major advantages of the historical information disseminated by NHGIS is that it is provided as standardized shapefiles, for use with GIS software. 

"Until recently, the data needed for assessing demographic change have
often been impossible to find, difficult to use, or too expensive to
obtain," note Borah and Schroeder. "With NHGIS and others making ever increasing amounts of
demographic data available through integrated systems that let users
assemble multiple years of data quickly, you will now be able to spend
more of your time analyzing data and putting it to use. Spending
valuable time aimlessly searching for needed census or GIS data
shouldn't be your job."