As the database editor, I am trained to turn something that looks like this:
Into something that looks like this:
But that only works for current demographics. Much of the nation's statistical history is stored in dusty bound volumes. The Census Bureau has been good enough to scan many key documents into PDF format.
Yet if you want to really study history through numbers, digital information is the gold standard. And fortunately, much of this information is being recaptured.
The University of Virginia has provided historical data for states and counties for several years.
But what's really exciting is an initiative at the University of Minnesota's Population Center to convert the most local of historical Census data to digital format.
What this site provides is detailed Census data down to the neighborhood (tract) level, and they give you corresponding maps to go with it.
Data and maps obtained from that effort enabled us to build the interactive history of Newark demographics for our coverage of the 40th anniversary of the Newark riots.
If you go to this page, check out, for example, the last link on the bottom right, vacancy rate. You'll see before your eyes a color-coded map showing the vacancy rate in Newark for 1960 and 1970. Change years, and you can see how the problem of abandoned housing spread over the decades.