swgohome.com

And back in 2003, I was in South Dakota when this took place: http://www.crh.noaa.gov/fsd/?n=tor2003jun24_tracks , which held the record for most tornado outbreaks in one state in a 24 hour period (67 tornados total).

I saw a video of this on the news too....it was an insane storm.
I think the deaths down there are at 300+ because of this.