There are some "natural lakes" along the Missouri river, and probably the Mississippi, that were formed when the river, in a rage, straightened itself out. All of them that I'm aware of are shallow and not really premium fisheries. There is a State Park in the northwest corner that is on one of these, can't recall the name. Most are all private. There was one on the river where I spent much of my childhood, it was in fact called the Old River and resembled a deep slow moving creek, except that it didn't flow. It was long and narrow, about 6' at the deepest and a couple of miles long. There was also another much smaller one that resembled a U in the same bottom.