Which radical union, founded in 1905, worked to unite the American working class?

The Industrial Workers of the World (IWW), founded in 1905, aimed to unite the American working class across various industries and occupations, especially those often overlooked by traditional labor unions. The IWW focused on organizing unskilled workers, migrants, and those in temporary employment, advocating for direct action and solidarity among workers of different backgrounds.

The IWW’s radical approach included the use of strikes and other forms of protest to achieve better working conditions and wages, distinguishing itself from more conservative organizations. By emphasizing unity among all workers, regardless of trade or skill level, the IWW sought to challenge the existing capitalist structure, promoting the idea that workers should collectively own the means of production.

In contrast, other labor organizations like the American Federation of Labor (AFL) primarily focused on skilled workers and negotiated through more conservative means. The Knights of Labor, while also seeking to unite workers, were less focused on direct action and became less effective after the Haymarket Riot in 1886. The American Labor Union is not a historically recognized major labor organization like the others. Therefore, the emphasis of the IWW on radical tactics and inclusivity among workers makes it the correct answer.