Statistics for occurrence #1 of “Mangan” in chapter 7 of The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 9: Poetry and Eloquence.:

... effort, and no one was more surprised than I was at the widespread and instantaneous popularity of the lyric I had been so strangely stimulated to write. Randall was always free to acknowledge that Mangan 's poem solved the meter of his famous lyric. The College boys to whom he read the poem the next morning were so enthusiastic that he at once forwarded it to the in which it was printed on April 26t...
Max. Freq. Min. Freq.
Entity Corpus Doc Corpus Doc  
James Clarence Mangan 4 4 0 0 0 user votes
J. C. Mangan 2 0 0 0 0 user votes
Patrick Mangan 2 0 0 0 0 user votes
L. H. Mangan 1 0 1 0 0 user votes
Richard L. Mangan 1 0 1 0 0 user votes

† This entity has been selected by the automated classifier as the most likely match in this context. It may or may not be the correct match.