Joseph Plaster traces the emergence and impact of Vanguard, a street-based activist organization forged in mid-1960s San Francisco by an unlikely coalition of sex workers, street queens, urban ministers, young adults, and War on Poverty reformers. Facing displacement, policing, and economic exclusion in the downtown "vice" district, organizers pooled food, housing, and medical aid while staging militant street theater and protests against a social order that treated street kids as disposable. Drawing on original oral histories and a newly assembled archive, Plaster follows Vanguard from all-night cafeterias to church basements to psychedelic shops. Its organizers developed drug-safety tools and published underground magazines while using federal antipoverty resources to establish experimental drop-in and employment centers. Vanguard's irreverent tactics and uncompromising sexual and gender visibility drew national attention, helping catalyze gay liberation and trans organizing while laying the groundwork for harm reduction and LGBTQ shelter activism. In Vanguard, Plaster recovers an electrifying history of mutual aid in action, showing how those pushed to the margins remade care, kinship, and political struggle.