The Industrial Workers of the World was founded at a convention in Chicago in June 1905, where some 200 radicals, socialists, and trade unionists gathered to build what William "Big Bill" Haywood, opening the meeting, called the "Continental Congress of the working class." Among the founders were Haywood of the Western Federation of Miners, the Socialist leader Eugene V. Debs, the veteran anarchist and Haymarket widow Lucy Parsons, the labor agitator Mary "Mother" Jones, and Daniel De Leon of the Socialist Labor Party.
The new union rejected the craft-by-craft model of the American Federation of Labor, which organized skilled workers by trade and largely excluded the unskilled, immigrants, women, and Black workers. In their place the IWW proposed "One Big Union" of all workers, organized by industry, whose ultimate aim was not merely better contracts but the abolition of the wage system and workers’ control of production. Its preamble opened with the words, "The working class and the employing class have nothing in common."