There is a White River in South Dakota. It ends by Ft. Pierre where it empties into the Missouri River. It goes through Mellette County, and there is a town named White River as well. It is often pretty white in color, thus the name. I have no idea if there are any fish in it, but if there are, there are not any like what you caught. If you drove across the state on I-90, you likely crossed it. It has been so long since I drove through there, I have no memory of it.
(Lakota: Makhízita wakpá; "White Dirt River")