You can browse free PDFs of the Statistical Abstract of the United States online going back over 100 years (under “Earlier Editions”). It is filled with data on population, commerce, education, and so on. Excellent for doing quantitative history — and not just boring things like how population size has changed over time. During the heyday of eugenics, from 1925 to about 1943 / ’44, there was an entire chapter entitled “Defectives, Delinquents, and Dependents”– they didn’t mince words back then! I haven’t gone through and collected a bunch of data from it yet, but there’s all sorts of fun shit like this in the Statistical Abstract. Did railroads become safer or more dangerous over time? If you’ve got a little free time, you can figure it out.
So far I’m the only blogger who’s done a lot with it, probably because no one else wants to waste the time to sort through all the PDFs and numbers from scanned PDFs into Excel. The more recent editions at least have digital PDFs that allow you to copy & paste, and the most recent ones have Excel spreadsheets all ready to download. Play around with it — there’s a lot to discover.