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.
Correction: There are several incarnations of the flag throughout the film, but none with 50 stars. The most common one has 34 stars -- 4 rows of 7 and one row of 6 in the middle. The filmmakers obviously took care to include authentic flags, it is unlikely that they would have let a "50 star" slip through.
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.
Correction: Amsterdam is trying to conceal his identity from Bill. He is probably not being entirely honest.
Corrected entry: What's going on with Daniel Day-Lewis' character? A man with one eye manages to throw knives with pinpoint accuracy? With one eye he'd have no sense of distance, so in reality he'd be an awful shot.
Correction: It can be done, it just takes practice, and if the eye has been missing from a young age it's not as much of a liability. I only have one eye but I can throw knives, darts, etc. just fine.
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.
Correction: Almost 50% of projectiles fired from cannons during the Civil War peroid were explosive in nature. These included cannon balls with burning fuses as well as cannisters that detonated on impact via a plunger device.
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.
Correction: In the beginning we see Liam Neeson's shaving in the mirror, so we see him cut his right cheek when he cut 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.)
Correction: The movie primarily takes place in 1863, when most firearms were using cartridge ammunition, or at least cap-and-ball ammunition, no ramrods or external primer systems required. You're describing muzzle loading firearms, from an earlier period.
Corrected entry: In the scene where Daniel Day-Lewis shows Leonardo DiCaprio how to stab a person, using a pig, Day-Lewis hands over the knife to DiCaprio. In the shot that actually shows the knife exchanging hands, the handle is black plastic. (00:54:55)
Correction: It's not clear if the hand of the knife is plastic or wooden or made of some other material. One cannot be certain about that.
Correction: The Brooklyn Bridge appears in the very last sequence of the film where the gradual growth of New York is shown from 1863 to our days ending with the Twin Towers shot. The bridge simply represents the first significant change of New York's landscape after 1863, which indeed occurred around 1870. Scorsese in no way intended to show it as a part of 1863 New York.