The Industrial Workers of the World was organized in 1905 by representatives of 43 socialist and trade union groups. The key organizers included William "Big Bill" Haywood, representing the Western Federation of Miners, Daniel De Leon, representing the Socialist Labor Party, and Eugene Debs of the Socialist Party.
The Industrial Workers of the World openly opposed U.S. involvement in World War I. The organization's leaders attempted to reduce the production of copper as an act of protest. Several leaders were arrested, convicted and sentenced to prison under the Sabotage and Espionage Act of 1917. Although the I.W.W. estimated it's membership at 100,000 members in 1912, by 1919 it was reduced to 30,000.