When George is to meet with Lincoln, the exterior shot identifies the location as the War Department. However, the interior rooms where they meet are definitely Lincoln's cabinet room in the White House, as well as the White House East Hall, in those days a reception area, and a private southeast corner room, today known as the Lincoln Sitting Room.
At the battle of Petersburg, when the Union army advances on the Confederate lines, Billy crosses on planks and climbs to the top of the trench. At the top, he grabs the Confederate flag (the Stainless Banner)and waves it around. The scene cuts to a distance, and now he's waving the "Stars and Bars". The scene cuts back and he's waving the "Stainless Banner" again.
It is commonly regarded as a mistake that Ashton's wedding photo contains color when color photography was not available at the time. While it is true that the type of photography at the time produced only black and white images, it was possible and even common practice to add color to photographs by tinting them by hand.
Billy Hazard is shown as a member of the 1st U.S. Sharpshooters, a.k.a., Berdan's Sharpshooters, throughout the war. However, Hiram Berdan was extremely strict about forming his regiments and companies by state. As a Pennsylvanian, Billy would have been assigned to Company C, 2nd U.S. Sharpshooters, the only unit in either regiment that accepted Pennsylvanians.
At various points throughout the series, people kept referring to the President's residence as The White House. During the time of President Lincoln, it was called The Executive Mansion. The term "White House" was not coined until the administration of Theodore Roosevelt.
After the First Battle of Manassas, President Jefferson Davis is seem in his office talking to Orry and saying, "There stood Jackson like a stone wall." Davis never said that. The remark is really attributed to Confederate General Bernard Bee who was trying to rally his frightened troops when he said, "There stands Jackson like a stone wall." According to some historians, this served as the turning point of the battle for the Confederacy.