I believe I heard the background story to this hymn when I was a teenager. By that point, I knew it was the Christmas hymn that was hard to play with its 3 flats and accidentals throughout. Also in ward choir we sang a version where the 3rd verse went into a minor key, which made that somber verse stand out even more, and its change to a major key in the 4th verse bring out the joy and hope in the author/singer's realization. Always, always loved the words of this song, particularly the last 3.
The song took on another special meaning to me when my first family ward on my own, without my actual family in it with me, had a magnificent pipe organ with these amazing chimes. It was a tradition in our ward to play this hymn on the Sunday we had our Christmas Sacrament program, with those chimes. In the last 2 months, the ward boundaries were reorganized and our ward ended up meeting in a new building, with an obviously inferior organ. Yet our organist still played this with gusto this morning, making those chimes work as well as she could. And I still enjoyed singing these words of hope, joy, and redemption because Christ brought that as His gift to us, He and His life being Heavenly Father's gift to us.
*"Had rolled along th'unbroken song"
*"The wrong shall fail, the right prevail"
*"Till, ringing, singing, on its way"
From the history book
Longfellow's original poem was 7 stanzas long, published in 1867. Original Verse 4 and 5 were more of the author's grief over the Civil War occurring in his country (United States) at that time. The original 3rd verse is now the last because they wanted the song to end on a more hopeful, optimistic feeling. I'm great with that!