The US IWPA is best remembered as the political organization uniting Albert Parsons, August Spies, and other anarchist leaders prosecuted in the wake of the 1886 Haymarket bombing.

Anarchists and revolutionary socialists (who in the vernacular of the day called themselves "Social Revolutionists")[4] were united by their disdain with electoral politics and piecemeal ameliorative reform.

[4] A popular orator and brilliant journalist in the German language, Most's arrival was celebrated by an enthusiastic crowd in the great hall of the Cooper Union Institute in New York City.

[7] In 1883, the split between the SLP and the social revolutionists and anarchist was formalized, when the groups held separate conventions, in Baltimore, Maryland, and Pittsburgh, Pennsylvania, respectively.

The October 1883 convention of the anarchists and revolutionary socialists held in Pittsburgh was attended by representatives of groups in 26 cities, including among them Johann Most, August Spies, and Albert R.

The convention adopted a manifesto known as the Pittsburgh Proclamation, declaring the organization for "destruction of the existing class rule by all means" and for the establishment of an economic system based upon "free contracts between the autonomous (independent) communes and associations, resting upon a federalistic basis.

Eastern delegates surrounding Johann Most argued in favor of the "propaganda of the deed"—individualistic acts of terrorism which would win alienated workers to the anarchist cause through the power of example.

[11] Meanwhile, the Socialist Labor Party withered on the vine, with its membership plummeting to just 1,500 and its National Secretary, Philip Van Patten, leaving a mysterious suicide note and disappearing, only to reemerge later in another city as a government employee.

[12] At its December 1883 Baltimore convention, the SLP took the extraordinary, albeit short-lived, step of abolishing the role of National Secretary altogether and adopting a particularly radical program in hopes of cobbling together some sort of organizational unity with the so-called "Internationalists" of the IWPA.

Although The Alarm continued to be published in Chicago for a time, sympathizers and advertisers were scared off by the harsh repression and public approbation meted out to the anarchist leaders.

[3] A few small anarchist groups survived, however, notably those surrounding Johann Most and Benjamin Tucker and their respective newspapers, Freiheit and Liberty, published in New York and Boston.