Demographic data from the U.S. censuses is useful to many areas of study. Social Explorer makes using this data for analysis or map creation easier. A team at Queens Univ. of CUNY has produced this set of maps from census data, 1940-2000. A certain level of data is freely acessible, while additional data (especially at the census tract level) requires a subscription (see Data Availability). Even what is openly available provides in interesting window on the nation's history.
A link to this site is included on the library website at: Reference Sources / Statistics / Social Explorer.