Historians usually consider the revived Ku Klux Klan of the 1920s to have been consistently opposed to labor unions and the aspirations of working-class people. The official outlook of the national Klan organization fits this characterization, but the interaction between grassroots Klan groups and pockets of white Protestant working-class Americans was more complex. Some left-wing critics of capitalism singled out the Klan as a legitimate if flawed platform on which to build white working-class unity at a time when unions were weak and other institutions demonstrated indifference to working-class interests. In industrial communities scattered across the Midwest, South, and West, white Protestant workers joined the Klan. In Akron, Ohio, the Klan helped to sustain white working-class community cohesion among alienated rubber workers. In Birmingham, Alabama, the Klan violently repressed mixed-race unions but joined with white Protestant workers in a political movement that enacted reforms beneficial to the white working class. But Klan attention to working-class interests was circumstantial and rigidly restricted by race, religion, and ethnicity. Ku Klux definitions of whiteness excluded from fellowship many immigrant and Catholic workers. Local Klans supported striking white Protestant workers when Catholic, immigrant, or black rivals were present, but acted, sometimes violently, against strikes that destabilized white Protestant communities. Ku Klux sympathies complicated urban socialist politics in the Midwest and disrupted the effectiveness and unity of the United Mine Workers. Lingering Klan sympathies among union workers document the power of reactionary popular movements to undermine working-class identity in favor of restrictive loyalties based on race, religion, and ethnicity.