Although it's no longer well known as a flashpoint, few things were as controversial during the late 19th century as the Haymarket Affair. Depending on one's perspective, the riots and the violence that ensued were the result of anarchist terrorists attacking law enforcement authorities with a homemade bomb that was detonated during a large public event, killing a police officer and wounding several more. Others who were more sympathetic to the plight of the people protesting for better working conditions that night in Haymarket Square in Chicago on May 4, 1886 portray it as a peaceful rally that was marred by a heavy handed response attempting to disperse the protesters.

What is clear is that the moments following the explosion were characterized by confusion and bedlam, as some people ran away and others ran toward the site. By the time the shooting was done, nearly a dozen lay dead, including a number of police officers, and makeshift hospitals were soon overwhelmed.

Citizens in the area began to cry out for justice, and police detectives poured through the city, making arrests and questioning thousands. As word spread about the attack, cities around the country went on high alert, concerned that they could be next. It was soon determined that a traditionally anti-American group was responsible for the attack, and many threatened mob violence against anyone who looked like they might be involved with the group. The press egged on those in the public with cries for revenge and justice. Eventually, the suspected perpetrators' trial began, a sensational event followed closely by many across the nation. Tensions ran high as those involved were prosecuted and defended, and when the jury convicted eight anarchists of conspiracy and some of them were sentenced to death, many rejoiced while others cried out that Lady Justice had miscarried the case.

Lost amidst the violence was the fact that the protests that culminated with the Haymarket Affair had come in response to previous labor strikes across the country, and controversial police shootings of some workers on strike, which took on a discriminatory undertone because many of the laborers were immigrants facing poor working conditions. It was against this backdrop that political anarchists also got involved, which muddled things and ultimately brought blowback against immigrant communities after the Haymarket Affair.

More importantly, workers and those advocating on their behalf were galvanized by the events to push for what they considered much needed reforms, many of which would come over the next few decades.