Career
In 1861 he wrote the song "The Bonnie Blue Flag," about the unofficial first Confederate flag, using the tune from "The Irish Jaunting Carolina." The song was extremely popular, rivaling "Dixie" as a Confederate anthem. The song lost some of its popularity when, late in the war, McCarthy left the South for Philadelphia, Pennsylvania. McCarthy is portrayed in a cameo role in the 2003 film God and Generals where he is played by actor Damon Kirsche.
He stands on an impromptu outdoor stage and sings "The Bonnie Blue Flag" to a gathering of the Army of Northern Virginia high command.