Continuity mistake: When Jack Barts is lying on the ground, right before Abe kills him, his right hand is empty. When he is lying in the casket and Adam opens his hand, there is Abe's pocket watch.
Factual error: When Lincoln is giving the Gettysburg address towards the end, the flag flying on stage with him is a modern fifty star flag. There were just over thirty states at the time of the address.
Factual error: When Abraham and Speed are hiding in the belltower, Speed bumps into the bell's pulley and it tolls loudly. The nudge wasn't hard enough for the bell's clapper (pendulum) to hit the side of the bell.
Continuity mistake: While Henry is talking to Abe in the bar after some time of training, we can see that his face has healed. However, in the next scene where he shows Abe the vampire targets, his face is as beat up as before.