In later life he published two volumes of poetry, wrote a number of plays, six of which were produced, and served as United States Minister to Turkey and to Russia. His most successful play was the verse tragedy, Francesca da Rimini, based on the story of Paolo and Francesca; it was first produced in 1855 and revived, with great acclaim, in 1882 and 1901. Most widely known of the patriotic verse he wrote during the Civil War was his ``Black Regiment'' (celebrating the charge of the Negro troops at Port Hudson in 1863), which moved Oliver Wendell Holmes to write him an enthusiastic note of praise.
Boker's poem, ``Our Heroic Themes,'' which he read before the Phi Beta Kappa Society of Harvard on July 20, 1865, contained one of the earliest tributes to Abraham Lincoln. It concluded:
''No king this man, by grace of God's intent:
No, something better, freemen, -President!
A nature modelled on a higher plan,
Lord of himself, an inborn gentleman!''