I was thinking of adding this song, and looked around. Found it was already on DT, but I thought the following facts are interesting.

It was written by one Daniel de Marbelle in 1887. According to Cyber Hymnal he had a most interesting career. Born in 1818 in France, he shipped on a whaler, then joined the U.S. Navy and served in the War with Mexico. Then he had a second career as a circus clown, the first circus clown according to the above source, with Barnum & Bailey. Having done that, he helped Buffalo Bill organize the Wild West Show.

The song was recorded, probably for the first time, on July 29, 1927 in Bristol, Tennessee, sung by Alfred G Karnes and recorded by Ralph Peer for the Victor label. Just like Ralph Stanley and his Soggy Bottom boys in the film.

Natalie Marchant's website claims that she wrote it (I don't know who she is.) Emmylou Harris's website says it is Traditional. I have heard a recent version which is a lot more powerful than Karnes's, but can't recall who recorded it.