Those charged with the assassination of President Lincoln were tried by a military tribunal. The courtroom is located in Fort McNair and open to visitors on August 2, 2014 as per the following announcement:
WASHINGTON -- Joint Base Myer-Henderson Hall announces its quarterly Public Open House of Grant Hall's historic third-floor courtroom, located on the Fort McNair side of the Joint Base in southwest Washington D.C., from 10:00 a.m. to 4:00 p.m. Saturday, Aug. 2, 2014. The courtroom is the site of the military tribunal, held from May through June 1865, of those thought responsible for the plot to assassinate President Abraham Lincoln.
During a recent renovation of Grant Hall, which was originally part of Washington's Federal Penitentiary from 1826 to 1881, the third floor of the building was restored to depict the courtroom as it appeared during the 1865 trial. Courtroom features were recreated based on artistic renderings and written descriptions of court proceedings. Some furnishings and artifacts on display are on loan from the production company of a 2010 historical film about the trial, and other artifacts and documentation are from the National Defense University Library.
Members of the public are invited to the Public Open House, which is free to attend. Please be advised, however, that the third floor courtroom is only accessible by walking up two flights of stairs. Due to the historical nature of the structure, the building has no elevator.