Corky mentions Parnell Square, in Dublin, to the housemaid. However, Parnell Square was still called Rutland Square in the 1860's.
Bishop Benjamin T. Onderdonk is portrayed in this episode, which is set in 1864. However, the real Bishop Onderdonk died in 1861.
A painting of a female nude in the Haverford home is an obviously altered copy and/or photo-shopped reproduction of Edouard Manet's famous and scandalous "Olympia" which wasn't even exhibited until 1865 in Paris, a year after the time setting of this scene in New York.