His posthumously published journals have been used as a historical source about the literary culture of Boston in the late 19th and early 20th century.

Sullivan was born on November 21, 1849, in a log cabin house on Charles Street in Boston, Massachusetts.

[1] Sullivan attended the Boston Latin School and expected to go to Harvard University as his father did, but both his parents died by the time he was 14, forcing him to find work instead.

He became friends with the actor Richard Mansfield, who in 1887 acquired the theatrical rights to Strange Case of Dr Jekyll and Mr Hyde, an 1886 novella by Robert Louis Stevenson.

He attempted one more stage collaboration with Mansfield, a drama about the Roman emperor Nero, but after its failure the two became estranged.