Mary Surratt's house remains as a historic museum in what was then Surrattsville, Maryland. The U.S. Post Office soon renamed the town Robeysville, due to the notoriety of the Surratt name. In 1879, Robeysville was renamed to Clinton, Maryland.
Robert Redford insisted that the actors stay in costume as much as possible so that the clothes would start to feel natural to them. Most of the actors complained about this at some point or other as the locations were unbearably hot.
The look of the film was influenced by early photographs of the period, many of which tried to introduce elements of color over sepia. Director of photography Newton Thomas Sigel attempted to emulate that look whilst restricting the use of bright, artificial light.
John Cullum had virtually no time to prepare for his one scene as it had only been written a day and a half before it was filmed. Indeed it was shot in just a couple of hours and edited that very same day.
Toby Kebbell plays John Wilkes Booth, the man who assassinated Abraham Lincoln. Kebbell is no stranger to this kind of role. He previously played Pausanias, who assassinated Philip II of Macedon (father of Alexander the Great) in Alexander (2004).
It was relatively simple for the Extras Casting Coordinator to find bearded male extras, as Savannah, GA is home to the Savannah College of Art & Design. An art school that has a large populace of bearded students. Many of them served as extras on the film.
James MacAvoy's double makes an appearance as one of the frightened couple in the audience during the assassination scene. Both the audience's reactions and the play itself were filmed almost three months apart on different sets.
The shots involving the audience watching the play were not filmed on the same day as the shots of the play itself but months later. The audience's reactions were shot on the same stage as the court room. The extras watched a little TV monitor of the play, while Robert Redford directed them, and a double stood in for Booth. The double split his pants when he fell from the "box window", and the footage of the extras laughing were a result of that.