The Bureau of the Census is responsible for many significant data products, covering topics as diverse as County Business Patterns and Longitudinal Employer-Household Dynamics. The Current Population Reports also provide population statistics, and can be accessed by subject here.
But in honor of Census 2010, this guide summarizes where to get Decennial Census information.
The sections of this guide are
New Jersey Data
The Constitution of the United States (Article I, Section 2) mandates that a count be taken every ten years in order to establish the correct proportional representation in the House of Representatives. The first Census was held in 1790, and has been held every ten years since then. Over time, the amount of information collected and published by the Census has gradually increased, as one can observe by either browsing the shelves in a library with an historical Census collection, or studying the file sizes of Census products online.
Early Censuses focused primarily on population counts, and differentiated between slaves and free population until the 14th amendment brought equality of persons (at least as far as counting was concerned). By the early twentieth century, questions about immigration, language, occupations, and more had been added. Special Censuses were instituted to provide more detail on sectors of the economy. The Census of Manufacturers began in 1905, Government in 1910, Agriculture in 1925, and so on. Finally, in the most recent Censuses, the number of questions asked has been reduced, as surveys, such as the American Community Survey, have taken over with more frequently updated results on detailed population characteristics. See Princeton's excellent guide for a detailed discussion of what questions were asked in each year. Also, a very comprehensive overview of Census information by year is provided by Columbia University Libraries.
Complete runs of the print volumes of the Census are held at Alexander Library in the Documents collection. Browsing print is an excellent way to understand the structure of the Census. Microfilm reproductions are also widely available. Publications such as the County and City Data Book and the Statistical Abstract of the United States provide useful extracts of Census information.
The Census Bureau is digitizing historical Census volumes. Although this project is not yet complete, a large proportion of the volumes are available here, along with the publication Measuring America, which describes the evolution of the Census.
After 72 years, the complete records of individual responses to the Census are released on microfilm. The complete 1940 Census will thus be released in 2012. This information is often used for genealogical research. Selected years are available in CD-ROM and Microfilm in Rutgers Special Collections, and complete runs are available at the National Archives Regional Centers in New York and Philadelphia. Searching the library catalog for subject headings like "New Jersey--Genealogy" will list these as well as other useful publications.
There are a few sources that provide retrospective access to early Census data in electronic form.
The University of Virginia's Historical Census Browser provides data from 1790-1960 down to the county level, along with tools for producing tables and maps.
Social Explorer is a subscription-based website that provides data from 1790 to 2000 in an easy-to-use format. However, some of data is freely available.
The Historical Statistics of the United States, Millennial Edition (HSUS), has an electronic version that is available at Rutgers. HSUS has Census data, along with many other specially researched data elements, but only at the state level. HSUS also summarizes pre-1790 statistics.
For researchers, ICPSR provides raw data files for Census summary data for individual years, in aggregate files, and for many specialized tabulations. Most material is only available to subscribing institutions. Special files from ICPSR provide tract level data for the 1940 to 1970 Censuses (search for the Elizabeth Mullen Bogue File).
The National Historic Geographic Information System (NHGIS) provides boundary files and associated data for Census results from 1790 to 2000. This page from Indiana University has useful links to historical census tract maps.
The Longitudinal Tract Database allows you to track boundaries across Census periods.
The CensusCD is a CD-ROM database, produced by the company Geolytics, that provides detailed information down to the tract and block level for the Census from 1970 to 2000. It is available at Rutgers on the Data Services workstations in the Alexander Library Reference Room.
For the 1990 Census, the first "born digital" Census products are released, mostly in CD-ROM. Now both 1990 and 2000 data are available via the interactive American FactFinder website. Factfinder is the primary gateway for current Census releases, and also allows quick navigation to both thematic and reference maps showing tracts and blocks.
Specialized databases produced by the Census are also available.
Recent Public-Use Microdata Samples (PUMS) are available directly from the Census. Microdata contain anonymized random samples of individual's complete census responses, and can be used to answer more complex research questions than the summary statistics. Microdata for earlier years can be found via ICPSR and IPUMS (the Integrated Public-Use Microdata Series project). Public-Use Microdata Samples created by IPUMS begin in 1850, but ICPSR also has electronic Census data in other formats going back to 1790. PUMS data is also available for the American Community Survey.
From 1960 on, the Depository program begins to influence the material distributed. In particular, maps of Census Tracts and Blocks were distributed to Depository Libraries. A guide to finding Tract and Block Data at Alexander Library is available. For 1990 and 2000, maps are also available in electronic form.
Electronic Files describing changes in Tracts between Censuses can be found here:
1790-1930 - Census schedules (full listings of names) available in microform. 1940 will be released soon.
1790-1840 - Summary data available in print Census, online PDFs, and extracted in several online databases (Social Explorer, ICPSR, Historical Statistics of US)
1850-1950 - Public-Use Microdata Samples (PUMS) available. Otherwise, same as 1790-1840
1960 - Tract maps distributed to libraries. Otherwise, same as above.
1970, 1980 - CensusCD makes detailed electronic data available. Otherwise, same as above.
1990 - First Census with substantial digital delivery. Libraries have extensive CD-ROM data and map files. Now American FactFinder delivers 1990 data and maps too.
2000 - Data and Maps from 2000 Census delivered primarily through American FactFinder.
2010 - Will also be distributed through American FactFinder. The same will be true for 2010 Census data. American Community Survey supplants Census for many of the "long form" questions.