The lyrics tell of the last days of the American Civil War and its aftermath. Confederate soldier Virgil Caine "served on the Danville train," the main supply line into the Confederate capital of Richmond, Virginia. General Robert E. Lee's Army of Northern Virginia is holding the line at the Siege of Petersburg. As part of the offensive campaign, Union Army General George Stoneman's forces "tore up the track again".
The siege lasted from June 1864 to April 1865, when both Petersburg and Richmond fell, and Lee's troops were starving at the end ("We were hungry / Just barely alive"). Virgil relates and mourns the loss of his brother: "He was just eighteen, proud and brave / But a Yankee laid him in his grave."
Ralph J. Gleason (in the review in Rolling Stone (US edition only) of October 1969) explains why this song has such an impact on listeners: "Nothing I have read … has brought home the overwhelming human sense of history that this song does. It's a remarkable song, just the rhythmic structure, make it seem impossible that this isn't some traditional material handed down from father to son straight from that winter of 1865 to today. It has that ring of truth and the whole aura of authenticity. There's pain here, there is a sadness here. In Americana land, it's a kind of a beautiful sadness.."
The most successful English-language cover of the song was a version by Joan Baez released in 1971, which reached #3 on the Billboard Hot 100 chart in the US, as well as spending five weeks atop the adult contemporary chart.
(Thanks to SingSnap for the backing track!)