Corrected entry: The young Amsterdam had very crooked teeth. Leo DiCaprio has much better teeth. I don't think they had braces back then, especially not in asylums.
Corrected entry: Near the end of the movie the Brooklin Bridge is shown. The year is 1863, and the Booklin Bridge wasn't constructed until 1870.
Corrected entry: In the background the flag on a wall has 50 stars. This movie is set long before the USA was comprised of 50 states.
Corrected entry: Towards the end of the film when Amsterdam and Jenny are standing in the graveyard observing both Bill the butchers grave and Amsterdam's father's grave. On Priest Valon's tombstone it says that he is from Dublin. Earlier in the film Amsterdam says that he is from county Kerry. County Kerry is in the western region of Ireland, while County Dublin is on the eastern region.
Corrected entry: Towards the end of the movie in the riot scene, canons were fired into the middle of the 5 points and exploded in fireballs in the street. Canon balls were made of steel or lead and were used to penetrate the hulls of ships or knock down walls. They were not flying explosive bombs.
Corrected entry: At the beginning, when Liam Neison is shaving, we see him cut his right cheek with the straight edged blade, but in the next scene, when they're fighting, the cut is on his left cheek.
Corrected entry: Every time you see a person or soldier holding a rifle or pistol, you'll notice that the weapon has no primer cap under the hammer (which means there is nothing to create a spark to ignite the powder) and (especially with the rifles) quite frequently has no ram rods (without which they cannot reload.)