I'd guess most New Yorkers have likely forgotten or maybe never knew about the Draft Riots that took place between July 13–16 of 1863 - and for many I'm sure they'd rather not be reminded. However, they were extremely violent and ugly disturbances that were the culmination of discontent at Lincoln's new draft law - to enlist men to fight in the civil war, which at that time was going badly for the Union cause.
A shortage of volunteers and recruits into the Union army forced Congress to pass the US's first ever conscription act on March 3, 1863, which authorized President Lincoln to draft citizens into military service or pay a fee of $300. The draft coincided with the efforts of the Tammany Hall Democratic machine to enroll Irish immigrants [loyal to Tammany politicians] as citizens, so they could vote in elections. Consequently, many immigrants suddenly discovered they had to fight for their new country.
However, although the main objection was to national service of any kind, the provision allowing men drafted to pay either $300 or supply a substitute as a "commutation fee" to gain exemption from service was hugely resented. The perception among the working class was that the war was now a "rich man's war". In reality, the draft was designed to spur voluntary enlistment and only 6% of those draftees actually served.
To avoid the draft, men formed clubs where if one was drafted the others chipped in to pay the commutation fee. Regardless of the intent of the $300 provision—as a means of securing some much-needed funding for the war effort or sparing the rich from serving. During the movie, 'Gangs of New York', the fictional Army Recruiter comments when swearing in Irish immigrants as citizens: "That document makes you a citizen, and this one makes you a private in the Union army. Now get out there and serve your country."
The main drawing of numbers [for draftees] was held on Monday July 13, 1863, but a furious mob attacked the assistant provost marshal's office. The rioters initially targeted draft offices and police stations but soon began to attack any blacks they came across. They became a scapegoat and the target of the rioters' anger; those who fell into the mob's hands were often beaten, tortured, and/or killed.
Initially intended to express anger at the draft, the protests degenerated into mob-driven rampage against the new Republican regime and any blacks unfortunate enough to be caught by them. The conditions in the city were such that Major General John E. Wool stated on the 16th, "Martial law ought to be proclaimed, but I have not a sufficient force to enforce it."
Using artillery and fixed bayonets, the military suppressed the mob, but not before many blacks were beaten, tortured or lynched, numerous buildings looted or destroyed, including homes in the Gramercy Park area, an orphanage for blacks destroyed, even P.T. Barnum's museum of oddities.
The police force proved unable to quell the riots, it was outnumbered and had to focus on minimizing its own losses. Control of the city was not re-established until after the arrival of thousands of federal troops, which included several regiments of combat troops pulled from the front lines in Pennsylvania, where Robert E. Lee's invading Confederate forces had just been halted at the Battle of Gettysburg.
With 165,000 combatants the Gettysburg campaign was the bloodiest of the war, with over 46,000 casualties, or one in four. These combat troops, faced with rioters refusing to fight for the Union cause were understandably angry and shot to kill as many of the rioters as they could. In addition the governor sent in the New York state militia, which had not been in federal service, and a section of the 20th Independent Battery, New York Volunteer Artillery from Fort Schuyler in Throgs Neck.
By July 15th, the mob still controlled sections of the city, but by dawn on the 16th, there were several thousand Federal troops in the city and the riot largely subsided.
The exact death toll is unknown, but according to several historians, at least 100 civilians were killed and at least 300 more injured; property damage was about $1.5 million.
Although there are claims that as many as 30,000 mainly Irish immigrants took part in the riots, this cannot be verified. However, of the 184 rioters arrested whose place of birth could be confirmed, 117 were born in Ireland, 40 in the United States and 27 in other European countries.
On August 19, the draft resumed. It was completed within 10 days without further incident, and under the watchful eyes of federal troops. Although far fewer men were actually drafted than had been feared, of the 750,000 selected for conscription nationwide only 6% actually went into service.
The draft riots are also portrayed in the novels On Secret Service by John Jakes and Paradise Alley by Kevin Baker.
In a final note, the Martin Scorsese film Gangs of New York, set in the years prior to and including the Draft Riots, attempts to depict "the birth of Manhattan and the way the different waves of immigrants have shaped the city's growth." One scene shows Union Navy warships firing on the city. That flatly didn't happen—no U.S. warships have ever fired on the city. One of Scorsese's less than stellar efforts.