Hmm, finally that cow logo makes sense.. ;)

I think your information might be a little out of date. The Sioux City stockyards have been closed for over 10 years: http://amarillo.com/stories/032802/usn_smelly.shtml

I grew up in Sioux City in the 80s and you could smell a little, but even then the stockyards were significantly scaled back from their 1924 peak. I was there a few months ago and there is no smell any more.

I make that drive at least six times a year. Still stinks to high heaven. It's about the only thing that makes my kids look up from their iPads. With the stockyards closed, perhaps it's a longterm residual smell, or processing plants that are still around?

On a side note, I wonder how many head of cattle were slaughtered there over time.