There have been sharks fished out of the Mississippi River near Alton Illinois, just north of St. Louis, recorded back in the late 1800s. Bull sharks, probably, since they can handle fresh water. With the locks and dams now it is less likely they can get through, but not impossible. Ah, a good example of transitionary specie. If these sharks don't get killed off by human pollution they will likely evovle into a shark that is completely adapted to living and spawning in fresh water.