That I did not know, so I looked it up and was surprised by the answer I found. The most expensive photograph ever sold at auction was one titled Rhein II by Andreas Gursky. Not only was I surprised by how much the photograph fetched, but I was surprised by how bland the image was.
Rhein II by Andreas Gursky
Obviously it is a photo of the Rhine River in Germany, but there are a few more surprising things about the picture. Gursky photoshopped it to remove the industrial skyline from the background and a dog walker in the foreground.
So, what was the selling price of this photograph? On November 8, 2011, it sold for $4,300,000!
Not only that, but I was surprised to see that six of the top eight priciest photographs sold since the recession began. You can see the Wikipedia list HERE.