I spoke with the historical consultant of The Gangs of New York, Tyler Anbinder, about this specific scene. He had a great many concerns regarding it (and the rest of the movie, more on this later!), specifically the new Irish immigrants becoming citizens right off the dock, and then being drafted right after they become citizens.

Firstly, citizenship did not happen immediately upon arrival in the US, even with nearly non-existent immigration laws. It was a two-step process that took several years: first the person would have to declare an intent to become a citizen in a sworn statement before a judge, then five years later would return to that court with two witnesses to support that he had been a "good citizen". Naturally, politicians (Tammany politicians) could grease the wheels a little for this process, but it would never happen right on the dock. The Minnesota Historical Society did a podcast on this topic.

Secondly, as to the draft, there were no recruiting stations at Castle Clinton. We know this because the Irish American published an article in July 1864 titled No Recruiting In Castle Garden . The article is about whether or not a recruiting station should be built where the boats arrive, and the general agent reports:

At the meeting to-day, I mentioned the matter to several of the Commissioners, and while on account of their being no quorum, and as no official communication had been received by this Board from the Board of Supervisors or any other body, there could be and was no official action taken on the matter; yet the opinion of the Commissioners was decidedly adverse to granting such a request, on the ground that it would be injurious to the country in interfering with emigration, as would be the case as soon as known in Europe; and would be confirmatory, to a certain extent, of the charges made in the British House of Commons, as well as in France and Germany, by rebel emissaries and sympathizers, that the armies were being filled by the forced enlistments of arriving emigrants.

I don't know if this is the proper place to talk about it, but there's a funny story about Tyler Anbinder meeting with Martin Scorcese to talk about the historical inaccuracies in the film. Maybe another time!

What you are describing rarely happened. It was unusual for Union recruiters to be drafting immigrants straight off the boat, and although it did occasionally occur, the ports were generally free of Union drafters ("Gangs of New York", n.a.).

But! Even though the Irish were not instantly drafted, they were subjected to unfair treatment. Because wealthier WASPs could afford to buy out of the draft (which was allowed in the Civil War and used by many people), poor people and immigrants made up a very disproportionate part of the draft. This resulted in some bitterness--why on Earth would an Irishman who has nothing to do with the war against the South take up arms? The Irish became so fed up with the draft that they burned their draft tickets in New York during one of the worst riots the city has ever seen.

There's also the way that the Irish were portrayed by the media at the time. The Irish were numerous, poor, Catholic, and concentrated, so they didn't meet most of the requirements to be considered "good" immigrants. WASPs, in a word, hated them. The media/cartoons made a deliberate effort to equate the Irish to blacks, a group on the lowest rung of society. They were given apelike features in cartoons and called, ahem, "niggers turned inside out" (Schecter 35). It's hard to fight a war that you not only have no historical ties to but also on the side that is making you out to be subhuman, which blacks were already seen as.

Many of the Irish felt they were being used to emancipate the slaves, a goal they did not share. Why would they care about an issue that never affected them during their lives? So you can imagine the reaction when Irish names were called out by draft officers at all, and far more frequently than expected. The Irish and African-Americans did not like each other for this reason--they competed for the same jobs, but the Irish felt like they were being made subservient to the African-American cause of emancipation.

So while Union officers did not normally recruit straight off the boat, the draft was instituted in 1863 and resulted in the draft riots and a general distaste for fighting someone else's war. It took until much later that the Irish were viewed favorably, in part because of a rise in income among Irish families and the introduction of other, more "foreign" groups, e.g. the Chinese, by Anglo-Saxon Protestants, the majority group in power.

If there are any issues with this response, please, please correct it. My only expertise in this field is a college class and a few scholarly sources, so believe me, I won't be offended!

Works cited:

"The Devil's Own Work: The Civil War Draft Riots" by Barnet Schecter

"The New York City Draft Riots: Their Significance for American Society" by Iver Bernstein

"'Gangs of New York': Recruiting the Irish 'Straight Off the Boat'"

a follow up question would be about something In the book Gone with the Wind where the Irish father was upset with the Irish immigrants taking bounty money offered for military service. What was this bounty and was it real or Margaret Mitchell's fantasy for the book?