I really like Richard's approach to a history. I also see it as a keelboat song which was passed along as such songs are. This easily explains the addition of the Missouri. As to the title name, certainly there are many variations as Elliot points out. However, as the folks who live in Shenandoah County, Virginia would be quick to point out, their understanding is that it means, "Daughter of the Stars" and refers only to the river which originates nearby.