Herbert Asbury's "The Gangs of New York" was published in 1928, and covers part of what was shown in the film. It is a fact that New York City had no formal Police Department until the 1850's, and was essentially lawless even after that (there were two competing police forces). It is also a fact that Irish and other immigrant gangs were opposed by "native" American-born gangs in regular street battles. The Civil War draft riots that Scorsese depicted also happened. In fact, an estimated 2,000 people died and another 8,000 were wounded in four days of rioting, making it the bloodiest civil disturbance in American history. However, Asbury's book makes no mention of a massive fight between the Irish and the "nativists" during the draft riots, nor of a bombardment by naval guns. He does say that military units brought cannon and howitzers into the streets, which helped defeat the rioters.