As the lobbying arm of the civil rights movement, the Leadership Conference on Civil Rights (LCCR)—which has operated since the early 1950s—was instrumental in the historic legislative breakthroughs of the Second Reconstruction. The Civil Rights Lobby skillfully recounts the LCCR’s professional and grassroots lobbying that contributed to these signature civil rights policy achievements in the 1950s and ’60s. Shamira Gelbman explains how the diversity of this interest group coalition both hindered and enabled lobbyists to generate broad-based support for reforms that often seemed risky to legislators. They coordinated their efforts by identifying common ground among member organizations, developing coalitional positions on substantive and strategic questions, and exhorting organizations to mobilize professional and grassroots lobbying resources accordingly. The result was to “speak with one booming voice” to ultimately help secure the passage of the Civil Rights Act of 1964. The Civil Rights Lobby concludes by reprising key lessons from the LCCR’s organizational development and participation in civil rights policymaking. Gelbman suggests new directions for research on interest group coalitions and explores how the Leadership Conference’s experience sheds light on the politics of the Second Reconstruction.