Miles wrote "God Save the South", under the pen name Earnest Halphin, which is considered to have been the unofficial national anthem of the Confederate States of America during the American Civil War.

In 1859 he scored his first success with the tragedy of De Soto, produced at the Broadway Theatre, New York City, and during the same season his dramedy, Mary's Birthday, was performed.

He was again in Europe in 1864 and, on his return, published in the Catholic World a series of charming sketches, Glimpses of Tuscany, and, in 1866, Christine: a Troubadour's Song, and a volume of verse, Christian Poems.

In 1859 he had been appointed professor of English Literature at Mount St. Mary's, in which year he married Adaline Tiers, of New York, and moved from Baltimore to Thornbrook, a cottage near Emmitsburg, where he lived until his death.

[3] In addition to works of creative fancy, Miles delivered in 1847 a Discourse in Commemoration of the Landing of the Pilgrims of Maryland, and, shortly before his death, contemplated a series of critical estimates on William Shakespeare's characters.