This dissertation investigates alliances across gender, race, and class in the dynamics of working class solidarity. The analysis examines the geographically bounded organizational networks, community spatial organization, and political cultures in Kansas City that resulted in a general strike in 1918. The general strike is historically unexpected because it occurred in sympathy with low-wage white and Black women with the support of white union men and middle-class clubwomen. The research is motivated by the following research questions: How do we explain unexpected coalitions across class, gender, and race in Kansas City from 1910 to 1918? What collective action processes and unique historical conditions explain the militancy and solidarity exhibited during this time period? Drawing on theories from social movements and political sociology, I do a longitudinal historical analysis and process tracing to answer the research questions. The data suggest that a temporally and geographically based meso-level network, what I call a "solidarity infrastructure," helps explain unusual working class solidarity across gender, race, and class. A solidarity infrastructure is a set of formal and informal links with the support of Euro American men and middle-class women across movements, which articulate and coordinate a cross-class contentious front, mobilizing support of working class formation and solidarity. The concept speaks to why some locations in specific times exhibit inclusive collective action, a theoretical problem not adequately answered in the dynamics of solidarity literature.