I love people with too much time on their hands.  They are the only reason why things like this map of Chicago homes color coded by when they were built ever see the light of day.  The data is by quarter century only, but you really get a good feel for how the city was built.  It would be a cool bonus feature if they would give each year a separate color.  Even better would be a time-lapse showing the buildings being built year by year.  You can also see the neighborhoods that were gentrified by identifying the areas where individual homes were rebuilt.  It’s pretty nifty.