At the ball where Abraham dances with Mary, the music playing is Estudiantina waltz, or Band of Students Waltz. The Estudiantina waltz, or Band of Students Waltz is a musical arrangement, made in 1883, by Emil Waldteufel, which would be his Opus 191, No. 4. Its melody was composed earlier in 1881 by Paul Lacome, with lyrics by J. de Lau Lusignan.
Little Willie is shown playing with toys in January or February of 1862. His toy fort is flying the Thomas Jefferson Flag - 15 stripes and 15 stars - which was never used after 1818. It is very unlikely that he has a 44-year-old toy or that his father President Lincoln wouldn't make sure he'd have the right flag.
Abraham expresses to Henry an interest in becoming a vampire hunter when he's about 20, i.e. around 1829. Henry shows Abe a magic lantern slide show including several photographic portraits in Daguerreotype style which was not around until about 1838, the date of the first known portrait photographs. In 1829, only the most primitive, experimental, still photographs requiring extremely long exposure times were possible.
Soon after Lincoln laments how through twists of fate he found himself at 50 years of age the father of a nation that was tearing itself apart while trying to be a father to a boy not much older than he was when he lost his mother, he is told that "3000 more [are] dead". The audio for that phrase does not match the visual.
When Abraham is thrown on the ground during his first vampire fight, he receives numerous scratches on his chest, his clothes are torn in pieces and covered in his own blood. When he wakes up in the bed there is not even a single wound or mark on his chest.
After Lincoln's first fight he has a wound on his right eye. After Henry teaches him that silver will kill a vampire, they are hanging out in a bar and the eye wound is gone. Next scene the two are looking at anachronistic photos and the wound has reappeared.
When Lincoln is on the boat coming into New Orleans, St. Louis Cathedral is on the upper right side of the river, that part of the Mississippi River is the only section that flows north. Meaning, instead of coming down the river from St. Louis the cathedral should be on the left, they were coming up the river from the Gulf of Mexico.
On the train Will Johnson is seen loading a cap and ball style revolver by inserting a ball into the rear of the cylinder. The cylinder would actually have been loaded from the front, each chamber like a small musket, with powder first and then a ball.
Lincoln is shown in his White House office, which is depicted as oval shaped. The Oval Office we know today as the president's office is in the West Wing, which is not part of the White House proper, and was not constructed until the 20th century (Taft was the first president to use it in 1909). Although there were two oval rooms in the White House proper, neither was used as the presidential office by Lincoln. In the 19th century, many presidents including Lincoln used as their office the room now known as the Lincoln Bedroom on the second floor of the White House. The room is rectangular, not oval.
Just after meeting Mary Todd while working in a small store, Abe receives a letter. While the narrator reads the letter aloud - "Your prescription awaits you at the local pharmacy. Ask for Aaron Stibble." - the actual letter says nothing of the sort.
After the battle on the horses and the roll down the hill, Abe loses the ax that is picked up and swung by Barts. The ax then hits a log next to Abe's head and it is clearly seen that it bounces against the log.
During the Plantation scene, there are multiple close up shots of Abraham and Speed watching the dancers from the outside, through windows. Clearly the reflections of both the slaves and the vampires can be seen in the glass. However, when Henry was explaining to Abraham Lincoln that vampires had a weakness to silver and could be killed by silver weapons, he also explicitly said they don't show reflections in *mirrors* and it can be assumed that it's because of the silver is used in mirrors to be reflective. They can show a reflection in reflective materials that aren't silver.