The United States Census has unveiled a very useful interactive sharing a bunch of demographic data from the past one hundred years.
English Language Learners would probably require a little initial guidance in figuring it out, but it would be worth the effort.
I’m adding the link to The Best Reference Websites For English Language Learners and to The Best Resources To Learn About The U.S. Census.
Interactive map from New York Post
Mapping America: Every City, Every Block
Browse local data from the Census Bureau’s American Community Survey, based on samples from 2005 to 2009
Distribution of Racial and Ethnic groups:
http://projects.nytimes.com/census/2010/explorer