Please check also this online image collection search tool: http://maps.lib.uic.edu/

Dominant race/ethnic groups of Chicago - click image above to enlarge - 

Introduction
U.S. Census data are one of the most popular and comprehensive data (both spatially and temporally) in the United States. For more information on Census data, please contact us at lib-maps@uic.edu.

Library Collection
Selected data collection at the UIC Library - Documents - Maps Section.

U.S. Census Bureau's Electronic Resources
(Call# HA201 )
As a U.S. Depository Library, UIC receives most of the electronic resources, such as CDs and DVDs. Use our online library catalog, UICAT, to locate items that you need.

GeoLytics' CensusCD Series
(Call# )
UIC-affiliated member access only. Probably the most comprehensive dataset available for the UIC GIS users on campus. Currently, data access is available only by appointment/email.  Please contact us at lib-maps@uic.edu for more information about this dataset.

Web Resources

General

U.S. Census Bureau
http://www.census.gov/
Census Bureau provides excellent tools and resources. A variety of downloadable data is available through the American Factfinder, and also from the HTTP site (warning: many are *raw* data, knowledge on database management software or statistical software would be required, such as Access or SPSS).

CIESIN - Archive of Census Related Products
http://sedac.ciesin.columbia.edu/plue/cenguide.html
One of the data archive projects by CIESIN (Center for International Earth Science Information Network). Good resources for both current and historical data sources.

Boundaries

U.S. Census Bureau: Maps and Cartographic Resources
http://www.census.gov/geo/www/maps/
Mostly relatively recent boundary files. Old, such as 1980, boundary files is only available from the original TIGER files, or visit the CIESIN site below to access some of 1980 boundary files.

ESRI: Censuswatch
www.censuswatch.com
ESRI's U.S. Census resource site - included are free boundareis, various line (streets, railroads, rivers) & points (landmarks, etc.) files and some demographic data (redistricting & SF1). Including hard to find "block" boundary files.

IL Dept. of Natural Resources - Illinois Geospatial Data Clearinghouse
http://www.isgs.uiuc.edu/nsdihome/ISGSindex.html
County, tract and blockgroup level boundary files for the entire state of Illinois. Files are in the E00 (ArcInfo interchange) format. Importing E00 files in ArcGIS - Import E00 files in ArcView 3.x (use "import71 utility" - search help file for more information).

HUD - Census Boundary Files Download Site
http://www.huduser.org/geo/summarylevel.asp
Unique "split" boundary files (tract/block groups) that supplement the Census boundary files are available from this HUD's website. There files were developed for community planners interested in working with census tract and block group data that splits by jurisdiction boundaries (summary level 080, 090 and 091).

CIESIN - Archive of Census Related Products
http://sedac.ciesin.columbia.edu/plue/cenguide.html
One of the data archive projects by CIESIN (Center for International Earth Science Information Network). Good resources for both current and historical data sources. 1980 block boundary files are available from this site. 

Historical

NHGIS: National Historical Geographic Information Systems
http://www.nhgis.org/
The National Historical Geographic Information System (NHGIS) is a project to create and freely disseminate a database incorporating all available aggregate census information for the United States between 1790 and 2000.

ICPSR: Inter-university Consortium for Political and Social Research
http://www.icpsr.umich.edu/
ICPSR member access only (including UIC affiliated members). Historical summary files are available for downloading. Use keywords to search data holdings, such as "census and 1970."

CIESIN - Archive of Census Related Products
http://sedac.ciesin.columbia.edu/plue/cenguide.html
One of the data archive projects by CIESIN (Center for International Earth Science Information Network). Good resources for both current and historical data sources.

HUD - State of the Cities Data Systems
http://socds.huduser.org/index.html
(May not be good for GIS analysis because data available from here are all at the city/metropolitan level.. but) A variety of historical data, including 1970-2000 census, are available from this HUD's website.

Census Variation

CTPP: Census Transportation Planning Package (1990 & 2000)
http://www.transtats.bts.gov/
Also known as "Journey to Work & Place of Work" data, this less-used CTPP provides data about workforce (for example, # of jobs by industry/occupation by census tracts & TAZ at minimum - not available from the decennial Censuses) and commuting patterns (i.e. means of transportations, a volume of residence-workplace flow). The original data come from the decennial Censuses (long form questionnaires), but are tabulated in a manner so that transportation planners can get a better picture on where people live and work. Originally started in 1960 as a part of special report series by Census Bureau, the electronic version of the dataset became available for the 1990 CTPP in 1995. See also this Federal Highway Administration's CTPP website. 

Free Geographic Databases: Shapefiles and Databases
http://www.uwm.edu/Dept/ETI/PurchasingPower/ETIshapefiles.htm
The UW-Milwaukee Employment and Training Institute provides free & ready to use Census data shapefiles for the continental United States. Unique dataset includes Workforce data (tract/bg/zip), Income data (tract/bg/zip), Business data (zip), and also "purchasing power" data (tables).