John Fabian Witt uncovers the hidden history of the Garland Fund, a foundation established in 1922 that invested in radical progressive causes for decades. The Fund, endowed by a young heir who rejected his family's wealth, supported projects that seemed marginal or dangerous at the time but eventually became mainstream: labor organizing, civil liberties, and racial equality. Witt traces how the Fund helped build the NAACP's legal strategy that culminated in Brown v. Board of Education, supported early ACLU cases, and backed labor movements that won workers basic protections. The book demonstrates how small investments in radical ideas can bear fruit decades later, as strategies developed in obscurity eventually find their moment. Witt, a legal historian at Yale, draws on previously unexplored archives to tell a story with contemporary relevance. In an era when progressive philanthropy again debates strategy, the Garland Fund's history offers lessons about patience, conviction, and the unpredictable path from margins to mainstream. This is the kind of hidden history that changes how we understand social change.