I didn't know this -- but when you fill out the US Census (which all of us did in 2010), the census information is kept confidential for 72 years (roughly the average person's lifespan). So earlier this week, the information from the 1940 census became public information for the first time.
Kansas City has a lot of history and a lot of old homes. I looked up our house, and was amazed to find out that our 1908 home had already been divided up into apartments as of the 1940 census. We had known it was divided into apartments, but had always assumed it was after WWII - but apparently it happened prior to the 1940 census. Based on the the census information, 11 people (including a couple of young married couples and 3 sisters all in their 60s) lived in 5 tiny apartments in what is now my home.
It is also interesting that our now very racially diverse neighborhood had not a single non-white person in 1940.
I'll warn you, it may take a fair amount of looking to find the information on here as the forms are a little clunky -- but it is interesting if you're interested in taking the time to do it.