Lemont Illinois got hammered in the 70s-80s, plainfield,il got blasted in the in the 90s - and in the 2012 era the tornadoes have swung south of I-80 or along that line.
This is a tiny fraction of the area that three gigantic walls are supposed to do something to protect.
Anyone who thinks that Man can build Tornado Killer Walls should ask themselves why we can't predict gigantic storms on a regular and professionally reliable basis less than three hours in advance , but can back "tornado killing walls" and saying the science is settled - this can be done.
I think we have a better chance of predicting an earthquake or volcano sometime in the next hundred years, than we do predicting how to stop tornadoes from hitting the midwest in the near future.