“You’re a Grand Old Flag” is an American patriotic march. The song, a spirited march written by George M. Cohan, is a tribute to the U.S. flag. In addition to obvious references to the flag, it incorporates snippets of other popular songs, including one of his own.
The original lyric for this perennial George M. Cohan favorite came, as Cohan later explained, from an encounter he had with a Civil War veteran who fought at Gettysburg. The two men found themselves next to each other and Cohan noticed the vet held a carefully folded but ragged old flag.