I just found out about the Pruitt Igoe public housing project in St. Louis this week. I've lived less than two hours away from St. Louis all my life and not once have I ever heard this mentioned. You'd think that something as big a deal as that might be even briefly mentioned in some history class.
Wikipedia
And here's a link to a documentary on YouTube that I actually watched in my Sociology class this week. It's very very good and well worth the watch.