Bolstered by a wave of immigration in the early twentieth century, a polyglot American Catholic Church struggled to forge a secure subculture in a society that regarded Catholics with suspicion. In the decades that separated the Roaring Twenties from Vatican II, Catholic Action inspired laypeople to participate in the work of the Church's hierarchy. In endeavors that ranged from religious education and liturgical renewal to labor activism and immigrant outreach, this movement permitted the Church to maintain its distinctiveness while simultaneously engaging with the wider American culture. In the aftermath of the Second World War, however, a new generation of Catholics increasingly chafed against the hierarchical ideal of Catholic Action and found in the Second Vatican Council's definition of the Church as the "People of God" a blueprint for more autonomous lay apostolates. For laypeople- and laywomen especially- the call to democratize church structures at parochial, diocesan, and national levels in the years immediately following Vatican II, led to an increasing detachment from the structures of hierarchy and authority that had commanded almost universal submission during the 1930s and 1940s. The resulting apostolates were all too often defined as much by their defiance of authority as by their supposed commitment to the "Spirit of Vatican II." Empowering the People of God: Catholic Action before and after Vatican II has been written to provide readers with an appreciation of how American Catholics at the grassroots experienced the evolving pattern of social and religious activism. Contributors use archival research to describe and interpret an array of lay movements across the United States during the middle decades of the twentieth century. In its profiles of Catholic apostolates in New York City, Boston, Washington DC, Chicago, Detroit, Pittsburgh, Atlanta, and San Francisco, this collection of essays explores the fate of a diverse array of groups, including recent immigrants and middle-class college women. Empowering the People of God demonstrates the pattern both of historical continuity and transformation within the contemporary Catholic Church in America.