The origin of the song is unclear, and there are many sets of lyrics.
Some lyrics may tell the story of a roving trader in love with the daughter of an Indian chief; in this interpretation, the rover tells the chief of his intent to take the girl with him far to the west, across the Missouri River. Other interpretations tell of a pioneer’s nostalgia for the Shenandoah River Valley in Virginia, or of a Confederate soldier in the American Civil War, dreaming of his country home in Virginia.
The song is also associated with escaped slaves. They were said to sing the song in gratitude because the river allowed their scent to be lost. (Source, where you will find further info and words.)
As far as I am concerned the first suggestion is the one and Shenandoah is a beautiful love song. Whilst it is not a song for a woman to sing you really cannot miss this beautiful version by the Norwegian singer Sissel
Another female version which send tingles down my spine for some reason.
Chanticleer render it very differently from most.
Finally this beautiful one by Paul Robeson
There is an Irish Tenors version. Unfortunately they think it is Shanandoah like the river Shannon so I have not included it.